He’s a tailor, a loner, out of place in Paris. He lives in a small apartment. Looking out his window, he sees another apartment building and focuses on one apartment, where an attractive young woman lives. “Rear Window”-like, he sits and stares for hours, for days. He learns she has a boyfriend. He learns her boyfriend is responsible for the recent death of a 22 year old woman in the neighborhood. He becomes concerned about her safety. He falls in love.
To the police inspector, who appears throughout the movie, the murder case in unresolved. The tailor, because he is such a loner, because he doesn’t fit in.
Eventually the tailor meets his neighbor. She learns how visible her apartment is from his. She learns that he has been observing her. She appears to be both horrified, and curious. They develop a (platonic) relationship. He believes that she finds him attractive. He believes he can save her, and must. He has a vacation home in Switzerland. They talk about going there. He buys her a ticket.
At the appointed time, he goes to the railroad station. She is to meet him there. She doesn’t show up. He goes back to his apartment, despondent.
When he gets there, he finds his neighbor and the police inspector in his apartment. The inspector holds the purse of the murdered woman. He tells the tailor that she has told him that he killed the girl. Will he confess? Clearly, she is trying to save her boyfriend, and perhaps always expected to turn attention to the tailor. The tailor is beyond shock. He turns. He runs. He goes to the roof. He jumps. He dies.
He had left a note for the inspector. The inspector finds the note. It proves how the boyfriend had committed the murder. It talks to the innocence of the neighbor. It talks about how he has taken her to Switzerland. Where they will live happily, and she will escape the dangers from her brutal, murderous boyfriend.
The story was written by Simenon. The movie is called “Monsieur Hire”.