This is a moving story of a father who loves his son so much that he sacrifices anything for him. It's not easy for Jacques to 'get out of the hole' and build a new life, and that he works hard all this time so that Eddy can be proud of his name, to start anew. However, since he is busy, he has no time to watch over Eddy so that Eddy falls into the clutch of drugs. Jacques doesn't need Eddy's mother to tell him that he is guilty. When Eddy tells him how proud he is to have an ex-gangster as his father, so that Eddy gets privileges in jail, Jacques tells Eddy that Eddy is wrong.
Years ago, Jacques could be freed from jail because he pretended to be crazy. This time, when Eddy tries the same thing, it backfires. Like the title "Comme un boomerang" - it makes all Jacques's efforts to save Eddy become useless.
Like in Victor Hugo's Les Misérables, where it's impossible for an ex-convict to shake off his past, it's the same here. Those who have worked for and with Jacques Batkin for years has forgotten his merit. When the news about Eddy comes out, they greet Jacques sympathetically when he arrives in the office in the morning. When it's known that he is an ex-gangster, when he arrives in the office, they pretend they don't see him. Later his father-in-law demands that the name Batkin is to be taken off from the company's name.
A year after Eddy's arrest, both father and son have been tired. For his last effort, as he cannot help his son with an honest way, Jacques contacts his old friends and arranges an escape for Eddy. He and Eddy will flee to Vesuvius, the Italian border. A radio reporter reports how the father and son are being pursued by police helicopters. Should they pity the Batkins? No one weeps for a police murderer, especially if the late police leaves behind 3 kids, says the reporter. However, in this movie, José Giovanni and Delon have successfully made us have pity on the Batkins.