Leo is a lost and emotionally broken young man due to the recent loss of his father. Affected by this trauma, he gradually sinks into a bottomless psychological abyss, becoming unstable with a self-destructive tendency. He decides to find the mysterious grandfather he has never met, Jacques Merone, to tell him of his son's death. Jacques is a former great boxing champion, now turned into a fierce and uncompromising coach. Widowed and without any news of his only son for several years, he is a bitter and reactionary old man, eaten away by hatred and loneliness. He has nothing left except his past glory and his old Parisian boxing club where he spends all his time passing on his knowledge with seriousness and rigor. The moment Merone learns about Léo's true identity, as well as the terrible news, he immediately rejects the young man, the latter awakening the memory of his greatest failure : his son.