Marc Billard, boss of a public works company, regularly visits his building sites with Monica, an employee who’s used to granting him her favours in cheap hotels. One day, as they’re driving back from such an escapade, Marc fails to notice a bus travelling very fast. In swerving to avoid him, the bus crosses the road and rolls over. But the couple drive on without a word.
Back in town, they learn that the bus was full of children, some of whom were killed. There’s also talk about a car which probably caused the accident. How do they go on living without saying anything, and, above all, without raising any suspicions?