Super Bowl XLVII is defined by something that happened off the field, that started away from the stadium. It’s remembered for the moment, shortly after the second-half kickoff, when half the Superdome went dark.

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For weeks before Super Bowl XLVII, Doug Thornton couldn’t shake the ominous feeling that swirled in his stomach. He couldn’t place it, either. But it was unmistakable. It had settled in his gut.

Based in New Orleans, Thornton is the executive vice president of stadiums and arenas for the venue management behemoth SMG, and since 1997 he has run the Superdome, host of as many major events as any venue in America. The Rolling Stones played there. Pope John Paul spoke there. Walter Payton ran there. Muhammad Ali fought there. Republicans held a convention there.

Hurricane Katrina ripped through there.

What happened on Feb. 3, 2013, well, that was different. It wasn’t as harrowing as Katrina; it wasn’t life and death. But it shook Thornton, 57, just the same. A game that had been billed in the media as the Harbaugh Bowl, with coaching brothers John (Ravens) and Jim (49ers) facing off, would instead be remembered as something else. Not as the final game in a Hall of Fame career for Ravens linebacker Ray Lewis. Not as the coming-out party for lethally cool Baltimore quarterback Joe Flacco.

Instead, Super Bowl XLVII is defined by something that happened off the field, that started away from the stadium. It’s remembered for the moment, shortly after the second-half kickoff, when half the Superdome went dark.

In the aftermath, Thornton struggled to sleep. He felt angry and depressed. He felt responsible for what had happened, for the longest 34 minutes of his life. “It was like somebody punching you in the gut,” Thornton says. “And even though it wasn’t our fault, it became our problem. That was the headline: BLACK EYE FOR THE CITY, BLACK CLOUD FOR THE SUPER BOWL. The whole thing bothered me for months.”

Thornton says this on a Tuesday morning in late October, inside a conference room in the very building that went dark. Today the Superdome is half-lit, but this time it’s on purpose. Thornton wears a navy suit and a neatly-pressed light blue dress shirt over his thin frame. He’s brought printouts: press releases, news articles, technical reports.

Over the last three years, one memory has stuck with him, from the morning after that Super Bowl. That’s when he sat with Charles Rice, the president of Entergy New Orleans, the company that supplies power to the Superdome. Neither man spoke that morning. “I was at the exact same table, in the exact same chair [I was sitting in] when our staff evacuated the Superdome for Katrina,” Thornton says. “And I was thinking: How can this be?

“Lightning has struck me twice.”

Eighteen months until kickoff

In the late spring of 2012, Entergy representatives approached Superdome officials: They wanted to replace the switchgears in the venue’s switchgear vault, which is less of a vault and more of a house. This particular house is fenced off and painted brown and located about a quarter-mile from the stadium.

The switchgears act as transformers. They take large amounts of power from nearby substations and decrease the supply, lowering the energy to manageable levels as they feed it into the Dome through two thick copper cables. Those cables run underground, from the switchgear vault to the Superdome’s electrical vault, and each cable supplies power to half the stadium through two feeds, the A and B, which then disperse that power through every electrical panel and outlet.

What’s important to know is that when Entergy replaced the switchgears, they wanted the Superdome to replace the cables too. Thornton didn’t think it was necessary; tests showed the cables were running at roughly 90% efficiency. But then something that an Entergy employee said changed his mind. “We want to avoid the Candlestick moment,” that person told him, referencing the 2011 Steelers-49ers game during which a blown transformer caused two power outages.

Thornton approved the work and the Superdome cables were replaced for roughly $500,000. According to Thornton, Entergy (which declined multiple requests for comment) spent $4.5 million on new switchgears.

Six weeks until kickoff

The Superdome played host to three football games shortly after replacing those cables: the Dec. 22 New Orleans Bowl, a sold-out Panthers-Saints contest on Dec. 30, and the Sugar Bowl, three days later. The level of power consumption at the Dome is measured in amps, or electric current, and the stadium can handle about 1,100 amps at any moment through either feed. (A normal operating load would max out closer to 480 amps.) Readings at those games peaked around 350 amps, far below the venue’s capacity.

Then the gremlins started to appear. Thornton uses “gremlins” to describe glitches in the system, and he first noticed them in the months before the Super Bowl. Like when CBS’s trucks arrived on-site and began tapping into whatever power sources they could find. One plug-in blew a fuse that shut down the Dome’s internal computer server.

In order to confirm which systems would still work on the emergency generator, officials had conducted a power-loss simulation about a month before the Super Bowl, in the middle of the night, with dozens of electricians and consultants present. They wanted to see what shut down when the power went out and the generator kicked in, and the list was long: video boards, coaches’ headsets, locker room lights—everything that wasn’t essential for the evacuation of the facility.

The test results were encouraging in that they didn’t reveal any major problems. Still, officials felt compelled to draw up a protocol for if the Dome lost power. They even wrote a script for the public address announcer to read: “Return to your seats. Stay calm.”

“Just in case,” Thornton says.

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Four days until kickoff

On the Wednesday before Super Bowl XLVII, Thornton recalls telling two of his senior executives, “I just don’t have a good feeling about this.”

Asked if he’s ever had a similar premonition, he laughs. “Katrina is the only thing I can [compare it to],” he says. “But we knew that was coming. We just didn’t know it was going to be that bad.”

What Thornton couldn’t figure out then was: Why the bad vibes? There were only two big differences between the pre-Super Bowl warmups that the Dome had hosted after the cables were replaced and the big game itself. One was the addition of an auxiliary press area on the west side of the stadium, which required additional power. The other was the annual Super Bowl halftime spectacle, featuring Beyoncé.

That show was initially scheduled to operate off the Superdome’s main power supply. Early in the week, the pop star had even conducted her rehearsals on house power—but that only produced more gremlins. Television crews reported that their sensitive high-definition cameras showed power fluctuations during the warmup.

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Then, during a round of routine light tests on Friday, one bank in the southeast quadrant of the stadium went out. Thornton emailed Frank Supovitz, who as senior vice president of events for the NFL ran the Super Bowl. Thornton proposed a radical solution: move the halftime show onto a separate power source. Supovitz, who was being followed by Armen Keteyian and his 60 Minutes Sports crew for a behind-the-scenes Super Bowl piece, took immediate action.

About one week before the Super Bowl, Supovitz had been part of a group—senior management officials for the game and for the venue; the head of NFL security; plus local fire and police representatives—that gathered inside a ballroom at the Hyatt Regency, one block from the Dome, to walk and talk through potential emergency or disaster scenarios. What if a truck overturned on a highway and released ammonia, shutting down half the exits? What if the crowd broke into a riot? “Everybody had to know what they were supposed to do,” says Supovitz.

Thornton, too, was at that meeting. “I came very close to suggesting we should run a power-outage drill,” he says. “I stopped just short. I didn’t want to jinx us.”

Ten hours until kickoff

Before heading toward the Superdome on game day, Thornton ate breakfast at the Hyatt with several NFL officials. There, Eric Grubman, the league’s executive vice president, sat at a nearby table. Had anyone asked Grubman that morning about his background, the 57-year-old would have told them that he graduated from the Naval Academy in 1980 and completed its nuclear submarine program. For his first job he served on the USS Boston as an electrical officer. (“This was during the Cold War,” he says. “It was Hunt for Red October. Quite a thrill.”) He was later co-president of Constellation Energy Group. And while such experience didn’t exactly pertain to his current job, that was about to change.

Thornton left for the stadium at 10:30 a.m. and walked the building’s perimeter, looking for anything amiss. The NFL’s command center, known as NFL Control, opened at 11. Kickoff was scheduled for 5:30 p.m.

For Supovitz, the evening represented the culmination of 3 1/2 years of planning. He had lived out of the Hyatt for the final month, traversing the stadium’s perimeter daily on a Segway. He’d overseen all temporary construction, the building of barricades and media compounds and the league’s fan-experience hall. On the morning of the game, he did his own perimeter check, again riding his Segway. Keteyian’s 60 Minutes crew trailed behind—that is, until their motorized golf cart came to an abrupt halt. It marked the day’s first power outage.

At this point, says Grubman, “I wouldn’t categorize anything as out of the ordinary.”

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Kickoff

The Ravens scored first, on the second drive of the game, and parlayed three Flacco touchdown passes into a 21-6 advantage at the half. Thornton, meanwhile, had an employee stationed in the bowels of the stadium, checking the amp levels on both feeds. Those readings came back in the 350-360 range. But just after halftime, officials decided to increase the chillers (think: air conditioning) in hopes that the air might clear the billows of smoke that Beyoncé’s show had produced.

Supovitz and Thornton (along with Keteyian and his cameras) watched that routine—”Crazy Love,” “Bootylicious,” “Single Ladies”—from inside NFL Control, six stories above the field, up near the roof. Performed with the lights out and running on outside power, Beyoncé’s act went all of 12 minutes. When it ended, officials turned the lights back on, and the television broadcast resumed. “Everything was good,” says Thornton. “Up to that point, the week had been almost flawless.”

The 49ers kicked off to start the second half, and Jacoby Jones, a New Orleans native, fielded the ball and sprinted 108 yards for another score. The Ravens led, 28–6.

Up in NFL Control, Keteyian’s cameras rolled, as they had for months. Producers had pitched the NFL on a segment back in October, and the league granted unprecedented access. 60 Minutes filmed the rehearsals, the meetings, all of it. Now, a final interview with Supovitz was supposed to be the easiest sit-down of all, the we-did-it coronation.

Thornton looked at his phone. Some of his emails had vanished. “The hair on the back of my neck stood up,” he says. “I had this eerie feeling.”

The blackout

Supovitz faced Keteyian for most of the interview, his back turned away from the field. Keteyian first saw the lights on the west side of the Superdome go out, over Supovitz’s shoulder, one minute and 38 seconds into the third quarter. “Uh oh,” Keteyian said. “That’s not good.”

Cameras captured what happened next.

Supovitz: “All right. We lost lights.”

Lance Barrow, CBS producer: “What happened?”

Mike Arnold, CBS’s lead game director: “Well, lights just went out on the field.”

Game officials forgot about the cameras, which continued to roll.

Thornton: “Frank, we lost the A feed.”

Supovitz: “What does that mean?”

Thornton: “That means about a 20-minute delay.”

Says Keteyian now, “The first thing that came to mind was the T-word.” And by “T-word” he means “terrorism.”

Elevators on the west side of the stadium went down, with fans trapped inside. Escalators stalled. Credit card machines stopped working at concession stands. The lights in the 49ers’ locker room went out. Emergency lights came on.

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In hindsight, the group in NFL Control remained remarkably calm. Given the circumstances, so too did the fans in the stadium. No one sprinted toward the exits. There was no commotion. Only confusion. “I was satisfied immediately that we had an operational problem, not a safety problem,” says Grubman.

The east half of the Superdome still had power, and officials immediately decided that, in order to decrease the amount of power they were still using, they would shut down everything inessential on that functioning side, including the air conditioning. They communicated via handheld radios and text messages and they carried handwritten notes down flights of stairs. “It was controlled chaos,” says Thornton. “Everybody in [NFL Control], we had drilled for this. After a deep breath, we knew what to do.”

Three minutes passed like an eternity—then the public address announcer read from the pre-written script. After seven minutes, he repeated the message. After eight minutes, NFL Control sent a text-message blast to fans who had provided their cell phone numbers for stadium updates. After about 17 minutes, the trapped fans were removed from the elevators.

Officials, meanwhile, scrambled to figure out what had gone wrong. They started by eliminating possibilities: Police ruled out a terrorist attack; Beyoncé was absolved. (“Everybody thought Beyoncé’s show had something to do with the outage,” says Supovitz. “It really didn’t.”) Thornton dismissed the possibility that a transformer inside the stadium had blown. Exactly one half of the Superdome had gone dark—the west side, which is powered entirely by the A feed—and that indicated an issue with the power supply. He immediately thought back to the replaced switchgears in Entergy’s vault and the cables that fed power to the Dome.

Thornton sent an engineer down to the stadium’s electrical vault to manually join one feed to the other. Based on the tests he’d run two weeks earlier, he believed the Dome could run off only the B feed (at least through the conclusion of the game). He yelled into a radio to start the procedure, but Entergy officials, who were at their vault a quarter mile away, interjected: They insisted they could restore power to the A feed instead.

“We can’t wait any longer!” Thornton shouted.

“[The director of engineering] is down there,” Thornton says now, “ready to flip the switch, and he’s all suited up like the Michelin Man. I’m screaming, and then, all of a sudden”—he snaps his fingers—“the lights come back on.

“I’m hyperventilating.”

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Power had been restored to the A feed after 18 minutes, and then the Superdome went through a system reboot on the west half, like restarting a personal computer. The scoreboards came back on, as did the video screens, the coaches’ headsets, the elevators and the escalators.

All the while, players milled about, stretching and throwing passes and trying to stay hydrated—anything to block out one of the strangest moments in Super Bowl history. Ravens guard Marshal Yanda says he and his teammates received little information about the blackout or when play would resume.

Flacco kept his arm loose. For the first time in his career, he scanned the crowd, looking (unsuccessfully) for his family. He wondered: How is it possible that on the biggest night in sports something like this happens?

One minute after the blackout

Following what amounted to a 34-minute delay, the second half resumed and the search for answers continued off the field. Already Entergy had denied responsibility, posting as much on its Twitter account. “I was very upset about that,” says Thornton. “Because no one knew.”

Supovitz gathered his staff in NFL Control. He went around the room, looking for assurances. He came to Thornton last. “I need to know that this is not going to happen again,” he said.

“I can’t promise you that,” Thornton responded. “I don’t know what’s wrong.”

Back on the field, the 49ers scored 17 straight points, whittling the Ravens’ lead to 28–23 by the end of the third quarter. “Obviously, the [break] didn’t go well for us,” says Yanda. “We were sluggish getting back in sync. The 49ers had all the momentum. We were reeling.”

As play continued, Thornton and Grubman migrated down to the Superdome’s electrical vault. Grubman, with his engineering and energy background, asked pointed, technical questions of Entergy staff members. “How can I say this politely?” Thornton says. “They didn’t have any really good answers for us.”

Grubman next sped toward the luxury suites to update commissioner Roger Goodell, who wanted the same assurances Supovitz had asked of Thornton. He got the same response. “He gave me that Roger Goodell face,” says Grubman. “It wasn’t the answer he wanted.”

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“Thanks,” Goodell told Grubman. “Do your best.”

The Ravens led 34–31 when the 49ers reached Baltimore’s seven-yard line. First-and-goal, 2:39 remaining. The Ravens then made four stops backed up near their own goal line; on the last one, a pass from Colin Kaepernick to receiver Michael Crabtree fell incomplete as San Francisco’s sideline clamored for a pass-interference penalty.

Baltimore’s sideline erupted in celebration as the final seconds ticked off. “Heck no, we didn’t care [about the power outage],” says Yanda. “After we won that sucker, everyone was going crazy. It didn’t bother me one bit.”

He adds: “Maybe it took some years off my life.”

One hour after the blackout

As the Ravens rejoiced in their locker room, Supovitz gathered his crew and apologized for a “tough day.” “We had a great week,” he told his staffers as the 60 Minutes cameras rolled. “We had a half-hour hiccup. The lights went off. They got plugged back in, we played the game.” A champagne toast followed.

Grubman and Goodell discussed the potential public relations fallout and decided to avoid assigning blame. “I didn’t see any problem on the stadium side,” says Grubman. “I thought the stadium performed admirably.” He told Goodell, “I wouldn’t point my finger at the [Superdome].”

Thornton, meanwhile, received the message around 2:30 a.m.: “Roger wants to see you.” He left the stadium and went straight to meet the commissioner at the Hyatt. There Goodell asked Thornton to accompany him to the league’s press conference later that day. He also inquired about whether there was anything that could have been done to prevent the outage. Thornton didn’t know. Not yet.

“I don’t want you to worry about this affecting your ability to host another Super Bowl,” Goodell told him.

One day after the blackout

At the morning-after press conference Goodell motioned for Thornton to sit next to him. He placed a hand on the Superdome honcho’s leg and reassured him that there was nothing to worry about.

Still, the Superdome hired a PR firm, Weber Shandwick. The 60 MinutesSports segment aired on Wednesday and Supovitz watched nervously. “Imagine having a bad day at the office,” he says. “Then imagine having your worst day at the office and 60 Minutes is standing to your left.”

Thornton couldn’t bring himself to watch. He still hasn’t.

The piece lasted almost as long as the delay (over 32 minutes), marking the longest segment in the brief history of 60 Minutes Sports. From inside NFL Control, the cameras had captured more calm than chaos. “[Supovitz] was the hero there,” Keteyian says. “Not even unsung.”

Six months after the blackout

In Sept. 2013, Ray Lewis floated the first conspiracy theory about the outage. He said he wasn’t going to “accuse nobody of nothing”—then started in with the accusations. “You’re a zillion-dollar company and your lights go out?” he begged incredulously. “No. No way.”

He added: “You cannot tell me somebody wasn’t sitting there, and when they said, ‘The Ravens [are] about to blow them out,’ [they didn’t say], ‘Man, we better do something.’ ”

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In an E:60 profile that ran a month later, fellow Ravens linebacker Terrell Suggs piled on, suggesting that Goodell had a direct role in the power outage. “I thought he had a hand in it,” Suggs said. “Most definitely, he had a hand in it.”

“I found it neither amusing, nor funny,” says Grubman. “Nor did it bother me. Consider the source. Passion doesn’t produce neutral analytics.”

If either player had taken the time to read the 15-page investigative report that was released that March, he would have found a far simpler explanation. The report was written by Dr. John A. Palmer of Palmer Engineering & Forensics, and while dense and technical, it makes clear what its author believes happened.

In an incredibly nerdy nutshell: The switchgears installed by Entergy in preparation for the Super Bowl contained a device called a relay that was supposed to shut down the power supply if either feed reached a certain amperage. The problem: The factory settings were too low. When the relay shut down the A feed on the night of the Super Bowl, it did, Thornton says, “exactly what it was supposed to do.” The Superdome could have handled more power than the factory settings had allowed for.

In a press release, Entergy said it wasn’t concerned with “whose fault” or “who was behind” the power outage.

Thornton thinks back to when the lights went out. Had officials run the rest of the game off the B feed alone, its relay would have tripped too. “Had that happened,” he says, “we would have had no lights.”

Three years after the blackout

The fallout from New Orleans started immediately and continues to reverberate. For Super Bowl XLVIII, held the next February in New Jersey, officials upgraded, inspected, backed up and tested MetLife Stadium’s power system months before the game. “I was not worried in that regard,” says Supovitz.

According to The Star Ledger, New Jersey governor Chris Christie told Goodell that if a similar incident occurred in his state there would be “bodies strewn in the parking lot for the people who are responsible—because that’s the way we handle matters.” (Christie had watched the Super Bowl in New Orleans from inside Goodell’s box.)

Supovitz left the NFL in June 2014 and now works as a special events consultant. He gives talks occasionally, the most popular of which is called “What do you do when things go wrong?”

New Orleans itself showed little ill effect from the episode. One study, by the University of New Orleans, found that Super Bowl XLVII had boosted spending in the city by $480 million. The merchandise and vendor sales during the blackout alone set NFL records for half-hour revenue.

None of that makes Thornton feel any better. On that Tuesday in October, he traverses down a stairway and enters through a door marked ENGINEERING, into the electrical vault. He points to a set of marks on the nearest wall, lines that once indicated how much water had accumulated from Katrina.

He turns right and heads into another room, this one housing two large gray boxes labeled “A feed” and “B feed.” This is where all of the power inside the Superdome is distributed.

Or, on one night in 2013, partially distributed.

“When I’m here alone, I often think about Katrina,” Thornton says. “I try to forget about the [Super Bowl blackout]. With Katrina, I’m amazed we didn’t lose more lives, given the circumstances—no running water, very little food, running on generated power for seven days.

“The power outage was a totally different thing. It was so sudden. I would almost give you the analogy of an earthquake. There are parts, when I look back on it, they’re hard to explain."

He stops talking and steals one more glance around the room.

“One day,” he says, “ I hope I can forget it.”