A young woman and her friend rent a room in an old dark mansion. Soon they become aware of the fact that the other "renters" are a very strange lot, and that there are some very odd goings-on in the house that seem to be centered in the attic.
- The episode opens as a young woman walks strangely through a dark mansion, arriving at the top of the house in the attic room. The door closes behind her, and she screams. Later, outside the mansion, a young man rings for admittance, presumably to inquire about a room for rent advertised via a sign in the window. An odd woman inside the mansion sees him ringing the bell, but refuses to admit him and he leaves, bumping into two young women on the sidewalk. Chrissie (Donna Mills) and Gillian (Judy Carne) are two young college students who ring the bell and are immediately greeted by Mrs. Ohxey (Althea Charleton). Mrs. Ohxey is extremely friendly to them, and she shows them an apartment that exceeds their expectations. When the girls worry that they won't be able to afford it, Mrs. Ohxey seems anxious to rent the space to them, and she gives it to them for a ridiculously low amount, telling them "I want you to have it!" Gillian and Chrissie move in and find a few peculiar things, such as a necklace with a pendant on it and the message "Help me, help me" written on the inside of the closet door. They begin to meet the other residents of the boarding house, all of them polite but odd in some unexplainable way. Unbeknownst to the girls, there are peep holes through which they're being watched. The residents also seem to be acting in unison: a man named Col. Wright (Peter Cellier) rifles through the girls' clothes while they are in the bathroom, stealing their underwear, while Mrs. Ohxey sees this and says nothing. Chrissie discovers a young neighbor boy peeping at her through a hole in the bathroom wall. All of the rooms are rented, but nobody is ever seen coming or going from the attic room at the top of the stairs. A pleasant young man named Jonathan (Alan Roberto) tells the girls that the room is inhabited by "Mr. C", and that he's the oldest resident of the house.
Chrissie acquires a kitten for the little neighbor boy, but the next day she is shocked to find its dead body in the garbage outside. The parents tell her that the cat fell from the window and they wanted to hide it before the boy could see. Gillian seems unconcerned about any of it, but Chrissie is more and more upset and suspicious. At a local pub, she meets the man who bumped into them on the sidewalk outside the house the day they rented the room: he introduces himself as Gary (Franics Wallis), and she tells him about the strange things that have been going on.
A man named Thurston (Clifford Parrish) arrives at the house and says he is looking for his missing daughter; he has a vague idea she may have stayed there, although he cannot be sure. Chrissie cannot find Mrs. Ohxey to verify it, so Thurston leaves a photograph of her and Chrissie promises to phone him after she speaks with Mrs. Ohxey. Ohxey denies ever having seen the girl, as do all the other residents, but Chrissie is positive it's the same girl because they seem to have found the missing girl's locket when they moved into the room.
Gillian is awakened in a trance one night by a voice calling to her from the attic. Chrissie wakes up and stops her from entering the attic just in time; the incident is dismissed as sleepwalking. Thurston arrives at the house to questions Mrs. Ohxey, and he is attacked by a figure that comes out of the basement.
Things come to a head when Gary takes Chrissie out of the city for a weekend trip, leaving Gillian alone. She is lured to a cocktail party, where she finds all the other residents in attendance except the mysterious Mr. C. The residents urge her to take a drink up to Mr. C, and she goes into the attic and is attacked. Meanwhile, Chrissie slips away from Gary and makes her way back to the city, unable to shake the feeling that something is wrong. She discovers Gillian missing, and when she searches the house, she goes into the basement and finds Gillian's dead body leaning out of a trunk. Terrified, she runs upstairs only to find Thurston. At first this comforts her; Thurston says he has phoned the police, but first he wants her to look in the attic. When she does, she is confronted by the mysterious Mr. C, a strange looking man. Mr. C is Mr. Cartney, a Satan worshipper who has been granted immortality. He seems to feed off the life force of the people he lures to the house. The house itself is mostly a figment of his imagination, and he wills his victims to see what he wants them to see. The residents are all his victims, long dead, and Cartney simply wills their images to exists as an illusion. This explains why all the residents had the same quirks and manner of speaking. They are really all Cartney, projecting himself in different ways. When he tries to attack Chrissie, Gary arrives and stabs him in the back with a shard of glass, but before the incident is over, it's become clear that Cartney has willed himself into the body of Chrissie, and she is now his living host.