Emile Paulon stole a car. Maigret's assistant Lapointe is shot and seriously injured while waiting outside the perpetrator's house. During his investigation, Maigret soon discovers that Paulon is not the shooter. His investigation leads him to the apartment building where the car thief lived. In the window of the apartment building on the opposite side, he notices a cactus, which will play an important role in this case. During Maigret's visit, the owner of the apartment, Françoise Bourcicault, pretends to be disabled. But the Commissioner is not fooled. With the help of Paulon's landlady, Maigret succeeds in finding the man behind the assassination attempt ... Based on the 37th novel in the Maigret series: Maigret en meublé (1951). Published in German translation under the title Maigret als möblierter Herr.