Based on J. B. Priestley's novel Benighted, five stranded travelers have to stay overnight in the old dark house of the strange Femm family.
Philip (Raymond Massey) and Margaret Waverton (Gloria Stuart) and Roger Penderel (Melvyn Douglas) in a terrible rainstorm manage to drive to an old house. The bearded butler Morgan (Boris Karloff) lets them in. Horace Femm is anxious about the landslide. His sister Rebecca (Eva Moore) reluctantly allows them to stay but says there are no beds. Horace says that Morgan is dumb and a brute. As Margaret changes her dress, Rebecca talks of sin and lust in the house's past. While they are having dinner, William Porterhouse (Charles Laughton) and Gladys DuCane (Lilian Bond) arrive and join them. William became a money-maker after his late wife was snubbed, and Gladys admits to being a chorus girl. She and Penderel go out to get some whiskey from the car. After the lights go out in the house, Horace and Philip go upstairs for a lamp. Horace is afraid of the upper stories. Morgan chases Margaret Waverton upstairs to her husband Philip, who fights with the drunk Morgan and knocks him out with the lamp. Philip says he heard a child's voice.
In the barn Penderel and Gladys have been talking intimately. They kiss, and to keep her feet dry he carries her back into the house, where they wake up William. Gladys tells him she loves Penderel. Upstairs the Wavertons find a very old man, who explains the savage Morgan is there to handle the dangerous and locked-in Saul. He is afraid Morgan might open Saul's door. Morgan seems to have done this, and Horace tells Philip to wait and kill him. Morgan comes downstairs and struggles with the three men while Rebecca repeats, "The sins of the fathers." Penderel puts Margaret and Gladys in a room. Saul (Brember Wills) comes down and tells Penderel he is not mad but that his family killed his sister Rachel. Saul picks up a knife and compares fire to a knife and ice. He says he loves Penderel and wants to kill him, as the biblical Saul felt toward David. Saul attacks Penderel and starts setting the house on fire. Saul and Penderel fight. Morgan breaks out of the cupboard and lets the women out; he finds Saul unconscious and carries him upstairs. Gladys discovers that Penderel is still alive. In the morning the Wavertons leave; Penderel wakes up to Gladys and asks her to marry him.
This film creates a mood of anxiety and fear of a brutal butler and an insane relative, while one night is enough to convince Penderel and Gladys they want to marry.