Steve’s path back to normalcy has not been easy. He has endured painful surgeries, weeks of intensive physical and cognitive rehabilitation in a hospital, and months more as an outpatient. He spent dozens of hours practicing social rules with Amber and playing brain-teaser games he had originally downloaded for his 6-year-old son. But many other people with similar injuries have tried all of these things, with much less effective results.

Ultimately, Steve’s recovery is a case study in all the ingredients, including luck, needed to restore a brain to its once-pristine state. Once he was injured, a series of events fell into place in just the right way: Paramedics brought him in from the train station where he fell to the hospital within minutes of his injury. The neurosurgeon on call that night happened to be one of the best in the state, and made bold decisions borne of her decades of experience. After Steve emerged from his coma, he gained admission into one of the best rehab facilities in the country, one that specializes in cognitive recovery. At the time of his injury, Steve was a 44-year-old mathematician in the best of health, and his body and brain responded beautifully to every treatment. For the crucial first six months after the injury, his job afforded him long-term disability and health insurance that kept his family free of financial stress. Amber had trained as a psychologist and redesigned their lives around Steve’s recovery. (Amber and I have been friends since our sons were 3, and I had met Steve a few times through her.)

“Everybody really did everything right, and he had a good result,” says Lauren Schwartz, the neurosurgeon who operated on Steve. “There may be people who should have had that result and didn’t. That’s what we can change.”

* * *

On December 13, 2014, the day of Steve’s injury, he said goodbye to his family at his Brooklyn home sometime around noon, and headed into Atlantic City for a day of gambling with four work colleagues. He had three or four drinks over the course of the afternoon, texted Amber silly pictures of himself smiling at the Borgata casino, and thinks he might have won money (she later found $1,000 in his wallet.) At some point, the men had dinner at Wolfgang Puck’s restaurant in the casino. Around midnight, they left the casino for the parking lot, but Steve went back in to use the bathroom and then returned to the car.

That’s the last thing he remembers.

Trying to piece together what happened next is an exercise in futility and frustration. Two of the four colleagues declined interviews, and have been uncommunicative with Steve and Amber. The other two offer variations of the same story. Both agree that the men drove through New Jersey in their rented car, listening to ‘80s music. Depending on who’s recalling it, Steve was either falling asleep and not tracking the passage of time, or awake and talking. The colleague who was driving dropped off one of the men, then drove the other three to the PATH train station in Newport, New Jersey, where they could take a train into Manhattan. At that point, they say, Steve was either asleep and had to be woken up, or was fully awake but tired. On the way down into the station, the men might have been running to catch the train. Or not. Steve might have fallen on the escalator. Or not. While on the platform, Steve might have tripped over backwards on a bag. Or not. He might have said, “Oh guys, I’m going to pass out.” Or not.