The owner of an apartment building is found murdered. Two rival policemen, Boucheron and Lambert, investigate the matter and get into the private lives of the tenants: an unfaithful judge, a crippled blind man and his daughter, an eccentric knife thrower, a shoplifter (and proud of it!), a bourgeois lady who has a bone to pick with a gigolo, a mistress who cheats on her lover, not forgetting the caretaker and a soldier in love...