I expected little from this movie because I was not a fan of action movies. I even thought the DVD cover was horrible: Laughing Alain Delon playing with a hand grenade. Since I didn't expect much, in the end the movie became not so bad. There are lots of action scenes (and violence!) in it, with great stunts done by 50 year-old Delon himself. He also sings the end-credits song.
The synopsis is as follows: Daniel Pratt (Alain Delon), is an ex-cop, who after the death of his wife (who had been murdered but the killer could go free due to lack of evidence), spends his life in Congo. His days are full of gambling and playing with the locals. He is happy, until a telegram arrives, announcing the death of his only daughter, who was in Lyon to study. Pratt returns to Lyon for a revenge and finds that a group of people, unhappy with the system, carry out their own justice. His daughter's death is an accident.
Also starring is Jacques Perrin as Inspector Reiner, Pratt's best friend. Pratt finds out later that Reiner is the leader of the vigilante group. I am not sure why Reiner commits suicide in the end. I think he created the group in the first place due to Pratt's wife case and when Pratt doesn't care about his mission, then all is lost.