When airline pilot Jed Towers (Richard Widmark) gets a letter from his girlfriend Lyn Lesley (Anne Bancroft) to break up with him, he goes to the hotel nightclub she sings at to get some closure. After Lyn says she’s breaking up with him because he isn’t understanding enough, Jed heads back to his room to spend some time with a bottle of Rye. Meanwhile, on the other side of the building, Eddie the elevator operator has gotten his niece Nell (Marilyn Monroe) a job for the night babysitting for a couple of hotel guests. After Nell gets the girl she’s watching, Bunny, to bed, she finds Bunny’s mother’s fancy robe and jewelery and because she was never allowed to have any of those things growing up, she can’t resist trying them on for just a few minutes.
Back in Jed’s room, he looks out his window and sees Nell in the negligee. He figures out which room she’s in, calls her up, and asks to come over and Nell agrees. Nell never tells him that she’s just babysitting for the night. When he gets there, he can’t quite figure her out and her explanations as to why she’s staying at the hotel just aren’t adding up. But since he wants to work on being more understanding, he gives her the benefit of the doubt. However, when Jed mentions that he’s a pilot, things really start to unravel fast. Nell had a boyfriend named Phillip who was killed in a plane crash and she starts to believe that Jed is actually Phillip. But then, Bunny wakes up and comes out to see Nell still wearing her mother’s things and starts causing a ruckus. Nell forces Bunny back to bed and orders her to be quiet. But when Bunny starts crying, Jed goes to see if he can take care of her and Nell opens the window for her when she complains of being hot, but Nell warns her again that she better not make any more noise. Nell believes that Bunny is trying to stop her from being with Jed, who she still believes is her dead boyfriend.
Jed has had just about enough for one night, but before he leaves, he notices some scars on Nell’s wrists and she confesses that she tried slashing her wrists after Phillip died. Just as Jed is finally ready to leave, there’s a knock on the door from Eddie, who came to check on Nell. Jed hides in the bathroom and Eddie is furious to see Nell wearing Bunny’s mother’s things. When he orders her to take them off immediately, Nell becomes even more unstable and hits him with an ashtray. Bunny screams again and Jed tends to Eddie while Nell quiets Bunny down by tying her up and gagging her. Only this time, some nosy neighbors come to see what’s going on. They’d seen men coming into the room and heard Bunny crying and came to make sure everything was OK. While they’re talking to Nell, they get the idea that Jed was holding them captive. Jed sneaks out while she’s talking to the neighbors, but he goes back when he realizes something wasn’t right with Bunny. When he gets back to the room, he unties Bunny and frees Eddie from the closet he had been locked into. When he gets out of the closet, Eddie finally admits that Nell had spent the last three years in a mental hospital. After they realize that Nell is now missing, they find her in the lobby with a razor blade, threatening to commit suicide. Jed manages to talk her down. Lyn witnesses the whole thing and is willing to give Jed another chance while Nell is taken to get the help that she needs.
For being the massive pop culture icon that Marilyn Monroe is, I think she is severely underrated in some respects. Specifically, in terms of how outstanding she could be in dramatic roles. In my book, Don’t Bother to Knock and Bus Stop are Marilyn’s two most underrated performances. Don’t Bother to Knock was Marilyn’s first attempt at serious acting and she did an excellent job with it. When playing a person with a mental illness, it’s so easy to make it over the top, but she played Nell with a great deal of restraint and vulnerability, which make her character all the more dark and disturbing. If you only know Marilyn Monroe for he comedic roles, then Don’t Bother to Knock is definitely worth seeing. You’ll really get a look at a whole different side to her. It’s also worth noting that this was Anne Bancroft’s film debut. Anne had a fairly small part, she spent most of her on-screen time singing, but she was a very nice singer.