Landis, raised as a Mennonite, said he had not yet told his mother. Nor had he told Tygart, the chief executive of the United States Anti-Doping Agency, with whom he had clashed for more than two years as Landis publicly fought his doping case.

But, Landis said, it was time.

“Lance Armstrong never came up,” Messick said in an interview last week. “But he did make a comment on the Mafia. He said, When you’re in the Mafia and you get caught and go to jail, you keep your mouth shut, and the organization takes care of your family. In cycling, you’re expected to keep your mouth shut when you test positive, but you become an outcast. Everyone just turns their back on you.”

Antidoping officials on multiple continents had pursued Armstrong for years, in often quixotic efforts that died at the wall of silence his loyal teammates built around him as the sport’s global king. Armstrong kept the dark side of his athletic success quiet, investigators and cyclists said, by using guile and arm-twisting tactics that put fear in those who might cross him.

But the lunch conversation between Landis and Messick would eventually be seen as the first significant crack in Armstrong’s gilded foundation, a critical turning point in antidoping officials’ quest to penetrate the code of secrecy that endured in cycling.

It set in motion a series of events that led to the stark revelation that Lance Armstrong, the seven-time Tour de France winner, and his United States Postal Service team were engaged in what antidoping officials called the most sophisticated doping program in history — one covered up by cyclists who banded together to protect themselves, one another and the ugly, deceitful underbelly of the sport.