Val Brosse, a private detective, receives Françoise, who confesses to him that she murdered her husband. The story is false, but Val, intrigued, decides to investigate.

1940: During the chaotic running fights of the French army the 7th company disappears - nobody knows they've been taken captive. Only their scouting patrol, three witty but lazy guys, can escape and now wanders around behind the German lines. They'd like to just stay out the fights, but a Lieutenant urges them to use a captured truck to break through to their troops.

18 June 1940: German troops sweep through France. The cavalry school at Saumer is ordered to withdraw, but the director resolves to stop the enemy on a 25km front with his students.