Servolle (Claude Brasseur) is a police inspector and Faguet (Jean-Louis Trintignant) is a real estate dealer who become good friends because of their shared love of bicycling -- something they do each Sunday with others of like mind, circling a wooded park area. While they are pedaling away one Sunday morning, Faguet's wife is murdered by a sniper that had been the target of Servolle's investigations for many months. Outraged at this tragedy, he vows to Faguet that he will find the killer. But as time passes, the inspector begins to wonder if Faguet did not curry his friendship in order to get him (Faguet) off the list as a suspect in his wife's murder. This preoccupies Servolle, as he discovers that Faguet has lied to him several times already.