Forty years ago to the week, the Red River Rivalry reached its acrimonious apex.

In the days leading up to the 1976 game, Darrell Royal, who had dropped five in a row to the Sooners, publicly accused Oklahoma coach Barry Switzer of spying on his practices. Royal was so mad, he challenged Switzer, assistant coach Larry Lacewell and the alleged spy, oilman Lonnie Williams, to take lie-detector tests to prove their innocence. If they passed, Royal offered to donate $10,000 each to the charity of their choice.

Switzer initially called the challenge "ridiculous." Then the day before the game, answered it was "worth more money to me to have [Royal] look for ghosts."

Switzer's dismissive response further exasperated Royal, who blurted out to AP reporter Robert Heard, "Why those sorry bastards, I don't trust 'em on anything."

The rancorous exchange, between legendary coaches in their final clash against one another, set the stage for one of the bitterest battles in college football history.

"Darrell made it known he didn't care much for us, Oklahoma and our staff," Switzer said. "And I understood it. Darrell had every reason to be upset.

"But the reason he was upset was because he was getting beat."

Turned out, Royal had good reason to believe the Sooners were spying on his practices.

Because they were. Four years earlier.

But first, the characters

In 1957, after a 1-9 finish, which included a 45-0 loss to Oklahoma in the Cotton Bowl, Texas called on a Sooner to save its floundering football program.

Darrell Royal had won three national championships at Texas when he faced Oklahoma in 1972. AP Photo

Born and raised in Hollis, Oklahoma, Royal arrived in Norman in 1946, the same year as Bud Wilkinson. With Royal becoming an All-American and one of his first key players, Wilkinson rapidly whipped Oklahoma into a juggernaut, highlighted by a famed 47-game winning streak through the '50s.

Royal followed in the footsteps of his mentor to become a coach, which brought him back to the other side of the Red River Rivalry. In his second season, Royal stunned Wilkinson's Sooners with a two-point conversion, which proved to be a turning point in the rivalry.

With Royal at the helm, the Longhorns returned to dominating in Dallas.

For Oklahoma, following two mediocre seasons under Wilkinson's right-hand man Gomer Jones and eight consecutive losses to Texas, the Sooners were on the hunt for a coach again in 1966. After an unsuccessful attempt to lure Royal, Oklahoma settled on Arkansas assistant Jim Mackenzie, who brought with him a promising offensive coach named Barry Switzer.

Behind Switzer's speed-oriented version of the wishbone offense that Royal assistant coach Emory Bellard had invented, the Sooners reclaimed control over Texas.

Chuck Fairbanks was in his first season as OU's head coach in 1972. University of Oklahoma athletics

In 1972, with Chuck Fairbanks leading Oklahoma following the death of Mackenzie, both squads entered the season with national championship aspirations. Texas boasted a terrific team headlined by the backfield duo of Alan Lowry and Roosevelt Leaks. The more-talented Sooners countered with star halfbacks Greg Pruitt and Joe Washington and a defense anchored by the venerable Selmon brothers.

And a little-known tackle named Derland Moore, who came to Oklahoma as a shot-putter, but would go on to produce the play at the center of the controversy between Switzer and Royal four years later.

The undercover agent

Royal understood that, though talented, his offense would have a difficult time moving the ball on the stalwart Sooners that season.

"We weren't quite on the level they were then," said Spike Dykes, then an assistant on Royal's staff. "They were a little more pronounced."

So the week of the 1972 game, Royal installed a quick kick. If Texas ran into a third-and-long, Royal would call for Lowry to punt the ball way, eliminating the possibility of a turnover or return while giving the Longhorns an upper-hand in field position.

Turned out, the Sooners were watching.

OU defensive coordinator Larry Lacewell would be the "handler" for the Sooners' spy. University of Oklahoma athletics

And waiting.

"Darrell four years later in '76 accuses us of spying," Switzer said. "There are semantics involved here. When I said me and my staff never spied on Texas, I was telling the truth. Because the spying actually happened in '72 when Chuck Fairbanks was the head coach."

That week of the 1972 game, Lacewell, the Sooners' defensive coordinator, suggested to longtime friend Lonnie Williams that he go to Austin and report back on the Longhorns. Posing as a construction worker, the perfect disguise with Texas' stadium under renovation, Williams covertly took note of everything the Longhorns practiced -- including the quick kick.

During a Friday walkthrough before traveling to Dallas, Lacewell brought the defense together to briefly practice one last thing.

"Coach Lacewell said, in case Texas tries a quick kick, this is how we're going to line up," Moore recalled. "We hadn't practiced against the quick kick in years. Then [Lacewell] walked by casually and said to me, 'Derland, move to the gap between the tackle and guard. ... You might have a chance to block it."

As Royal had predicted, the game turned into a defensive struggle. Trailing 3-0 in the third quarter and facing a third-and-long, Royal called for the quick kick.

But as the Longhorns broke the huddle, the Oklahoma defenders began hollering "quick kick" to Royal's disbelief.

"Lacewell already knew they were working on that because he got it from Lonnie Williams," Switzer said. "Well, we had our tackles, Raymond Hamilton and Derland Moore, inside the B-gaps to rush the punt. We had our 9-techniques hold their ends, who were going to be covering from a tight formation. And we had our safety run back to be able to return. So we're holding up coverage and we put a block on. When they came out and shifted to quick-kick formation in the end zone, well, our guys told everybody what the hell to do.

"Darrell four years later in '76 accuses us of spying. There are semantics involved here. When I said me and my staff never spied on Texas, I was telling the truth. Because the spying actually happened in '72 when Chuck Fairbanks was the head coach." OU coach Barry Switzer

"We looked like the best coached team in the world. ... But we wouldn't have known about the quick kick unless Lonnie Williams had seen the practices and told Larry about it."

At the final second, Moore remembered what Lacewell had told him, and took a step to the inside. Moore barreled through the Texas line to block the punt, end Gary Baccus cleared out Lowry, and Lucious Selmon pounced on the ball for a touchdown.

"Whether Derland had an inside secret, I don't know," Selmon said. "But I was sure glad he did what he did."

The defensive touchdown catapulted the Sooners to a 27-0 rout, which proved to be Texas' only loss of the season. And cost Royal the shot at a fourth national title. Instead, USC captured the national title, and the Longhorns finished third in the polls, a spot behind the Sooners.

With suspicions only later realized, OU defensive lineman Derland Moore used the quick-kick intel to block the kick and break the game open. University of Oklahoma athletics

"It seemed like one of those freak things that happen in a game," Leaks said.

Royal was dumbfounded by the block. "I know a lot of folks who paid $7 will question the quick kick," he said afterward. "I didn't think it would be expected."

Moore, however, began to get curious when he said Oklahoma defensive line coach Jimmy Johnson instructed him to "say nothing about the quick kick" to reporters.

"Something felt kind of suspicious about it," Moore said, "but you really didn't have much time to dwell on it because here came the reporters."

Moore only confirmed his suspicions much later while reading about it in a book.

Royal, however, would find out much sooner.

The spy comes in from the cold cocktail bar

For years, Royal has been suspicious that Oklahoma had been spying on his practices. But he never had any proof -- until the fall of 1976.

Tony Herry, a Houston businessman and Texas booster, was having drinks one night in Houston in December of 1975 with Lonnie Williams. As Herry told it, Williams, after a few cocktails, began boasting of the time when he pretended to be painter working on Texas' stadium to spy on the Longhorns practicing on the quick kick.

Herry relayed the account to Texas assistant David McWilliams, who passed along the information to Royal.

"It took three years for this to get back to Darrell that had happened because Lonnie Williams kept bragging about it," Switzer said.

Royal believed he finally had his proof. And the week of the 1976 game, he charged Switzer with spying, bringing the rivalry to an unprecedented level of animosity not even the leader of the free world could smooth over.

Moments before kickoff, President Gerald Ford, who was there for the coin toss, stood between Royal and Switzer in the tunnel.

University of Texas athletics

"[Ford] was trying to carry on a conversation, and Darrell and I weren't having it," Switzer said.

As the three walked out to the south end zone, one Sooner fan cut the tension. Or maybe added to it.

"This damn redneck from Oklahoma," Switzer recalled, "stood up and screamed, 'Who are those two a--h---- with Switzer? Of course, everybody started dying laughing. It wasn't funny to me, though. It made me feel like two inches tall."

Fittingly, perhaps, that game ended in a 6-6 tie, as Oklahoma flubbed what would've been the game-winning extra point.

"The best defensive game I've ever seen," Dykes said. "Just an all-out fight."

Afterward, Royal said the game felt more like a loss than anything.

"I wouldn't be sitting here with my belly about to throw up if I thought we had won," he told reporters. "I don't feel too good."

The spying controversy didn't die after the game.

Lacewell joked that he would take the polygraph for $300,000, which didn't amuse Royal, who said that was Lacewell's price to get out of coaching.

"Because that's what he'd have to do. I'll tell you what, I'd quit coaching if they'd take it and pass it."

Instead, Royal wound up retiring after the season.

"I never felt as sick about a game as I did that one," he would later say.

"I wanted that game more than any I competed in or coached in."