With the help of an "idiot scout", Brochant manages to find a "gem", François Pignon, a Finance Ministry employee whose passion is building replicas of landmarks with matchsticks. When Brochant starts to suffer from a bad back, his wife, Christine, leaves him shortly before Pignon arrives at his apartment. Brochant initially wants Pignon to leave, but instead becomes reliant on him, because of his back problem and his need to resolve his relationship problems.
He solicits Pignon's assistance in making a series of telephone calls to locate his wife, but Pignon gaffes each time, including revealing the existence of Brochant's mistress, Marlene Sasseur, to his wife Christine and inviting Lucien Cheval, a tax inspector, to Brochant's house where, in an attempt to disguise his tax evasion, Brochant is forced to quickly hide most of his valuables.
In the meantime, Brochant is able to make amends with an old friend, Just LeBlanc, from whom he stole Christine, and through the evening's events is forced to reassess his mistakes.