When a phony investment scheme perpetrated by Gustav Dupont leaves a group of Frenchmen bankrupt, some of the fleeced investors-- Professor Menard, country banker Pignolet, and a boxer named Welton--hire detective Albert Latour, a former army captain, to investigate. After learning that Dupont is trying to sell his wife Helene's chateâu to a garbage company, Latour decides to kidnap Helene and hold her for a large ransom. Masquerading as eccentric country doctor Germond, Latour tells Dupont that he wants to purchase the chateâu for twice the sum offered by the garbage company. Dupont invites Latour to the chateâu for a weekend, but is unable to convince Helene to give him control of the property. Meanwhile, Menard, Pignolet and Welton prepare to kidnap Helene as Latour has arranged for them to do. Still disguised as Germond, Latour visits Helene in her garden, and Latour's partners kidnap her and knock him unconscious in the process. Later, Dupont discovers a dazed Latour with a ransom note. Aware that Dupont is desperate to find Helene in time to make the sale, Latour suggests that he hire "Latour" to investigate Helene's disappearance. After learning why she has been kidnapped, however, Helene escapes from her captors, returns home and asks Latour to help her leave her husband. Anxious to close the deal now that Helene is back, Dupont telephones the real Germond and asks him to come to the chateâu. Latour intercepts Germond at the door and tells him that Dupont is insane, his particular obsession being selling his property at a profit. To calm the supposedly frantic Dupont, Germond offers to buy Helene's property for a huge sum. Helene then asks Dupont for a large sum to transfer her rights to the chateâu to him. When Latour's three friends show up to alert Latour to Helene's escape, they mistake Germond for their leader, but the quick-thinking Latour tells Dupont that the men are guards and have come to take Germond to the asylum. When Dupont finally finds out about the ruse, he declares his intention to divorce Helene. After she repays the investors with the money from the transfer, Helene and Latour leave to visit her mother.