Romain. a 28-year-old engineer working for a major industrial group. is named manager of a factory employing 300 workers in his home town. His father Serge. whom he hasn't seen since the death of his mother two years earlier. works as a simple labourer in this factory.
The reunion of father and son is difficult. Romain discovers Serge has a new live-in companion. Mylène. who has a son. Tom is Romain's age. unemployed. and now living in Romain's old bedroom in the family home. He kills his time kicking around with a band of half-hearted garage musicians. As for Serge. he's never felt comfortable with Romain since he "joined the enemy camp" and become an executive. And he naturally has a hard time accepting him as a boss.
The first few weeks are encouraging for Romain. He sets up the plan for restructuring the factory. And Serge's pals appreciate the new manager; even Serge gets closer to his son on the occasion of a bicycle race that brings them all together.
But before long. the group's top management cancels the scheduled financing and Romain is forced to prepare a work-force cutback. He announces the bad news to the labourers and their reaction measures up to their disappointment: impassioned and violent. Considering his son's about-face a personal betrayal. Serge leads the workers' fight. One evening. Romain has to face an angry. unruly group of workers and Tom comes to his rescue. The two young men go out on the town together. and - against all odds - a friendship starts to grow.
Thanks to Tom. Romain finds new energy and battles on all fronts as he negotiates the labour cut-back. He succeeds in getting support from the city authorities. and with the approval of the unions. manages to avoid all lay-offs through re-employment and pre-retirement plans (Serge is included in the latter).
The situation at the factory is now under control. and Romain begins to wonder about his odd new friend Tom. They're so different. and yet so much alike. Then a local photographer digs up an old snapshot taken in front of the factory - Serge. surrounded by a group of workers. is holding a baby in his arms. But the picture was taken in June 1959. before Romain was born.
As it just so happens. Tom's father is officially "unknown." Romain forces him to talk. but Tom's tears tell the whole story - the two men are brothers. Serge is father to both of them. the brilliant engineer and the "eternal knock-about".
Romain has resolved a long-buried mystery from his family's past. His relationship with his father is now on a better footing. And he is at last prepared to begin life anew. as an adult.