A group of apparent strangers must solve a murder mystery at a dinner party.
In New England in 1954, Wadsworth drives up to the Hill House off route 41, driving a vehicle with Washington, DC license plates and uses a key to enter the property. He then follows a winding path up to a large mansion. He gets out of his car and throws two bones at the German Shepard guard dogs and accidentally steps on dog poop before entering the mansion. He walks over to Yvette and asks her if she is ready and walks away. He then checks with The Cook to make sure dinner will be ready. The first guest to arrive is Colonel Mustard, and Wadsworth takes him to the study. Mrs. White is next to arrive and she is also brought to the study. Professor Plum, who is also going to the dinner party picks up a stranded Miss Scarlet, whose car has broken down on the side of the road. Mrs. Peacock is next to arrive and is introduced to Colonel Mustard and Mrs. White. Mr. Green arrives followed by Miss Scarlet and Professor Plum. Wadsworth gathers them all together and tells them that they have all been given pseudonyms and then dinner is ready. One seat is left open for Mr. Boddy, another member of the dinner party. Mrs. Peacock starts the conversation and it is discovered that all the guests either live or work in Washington, D.C. Mr. Boddy arrives and is introduced to the guests.
Mrs. Peacock demands to know why they were asked to come to Hill House and Wadsworth reads the letter he received which mentions that Mr. Boddy will end a long standing confidential financial issue that has plagued them, they then walk over to the study. Wadsworth opens a letter and tells him he has been ordered to inform them of what they all have in common. Mr. Boddy gets up and tries to leave and they find out all the doors have been locked and the windows barred. Mr. Boddy is about to break a window open with a ceramic pot when a Doberman Pinscher lunges at the window. Mr. Boddy is brought back to the study and Wadsworth tells the gathered guests that they are all being blackmailed by the same person, Mr. Boddy. A fight breaks out and Wadsworth tells them the police are coming. Mr. Body brings his bag from the hall and hands each of the dinner guests a wrapped boxed, which contain an assortment of possible weapons. Mr. Boddy tells the guests that they have a choice, they can expose him and also be exposed or kill Wadsworth. Mr. Boddy turns off the lights and a gunshot rings out. The lights are turned back on by Mrs. Peacock and Mr. Boddy is found lying on the floor.
Professor Plum checks Mr. Boddy and tells the others that Mr. Boddy is dead. A scream rings out and the guests run to the billiards room where Yvette is and Wadsworth takes the recording. Wadsworth tells the guests that Mr. Boddy was black mailing his wife after he found out that she was associating with socialists. He says that his plan was to bring them all together so they could all work to get Mr. Boddy arrested. They are reminded The Cook is still in the house and when they look for her they find her dead in the kitchen with a knife in her back. They drag The Cook's body into the study and find Mr. Boddy's body gone. Mrs. Peacock opens the door to the restroom and Mr. Boddy's body falls out towards her. The bodies of The Cook and Mr. Boddy are stacked on the sofa in the study. Wadsworth takes the remaining weapons and locks them in a cupboard and locks the door. As he goes to throw the key away, The Motorist is standing at the front door. He tells them his car has broken down and he asks to use the phone. He is taken to the lounge and locked in and Wadsworth throws the key away. Colonel Mustard suggests they split up to find out if there is anyone else in the house. Wadsworth cuts match sticks to decide who will pair with who determined by matching length matchsticks. Miss Scarlet and Colonel Mustard are paired up, while Mrs. White and Wadsworth are paired up leaving Yvette to pair up with Mr. Green and Professor Plum to pair up with Mrs. Peacock. Each pair then awkwardly search different areas of the house. An unknown person takes all the evidence that Mr. Boddy was using to blackmail the dinner guests and the recording and throws it into the fireplace, they then unlock the cupboard with the weapons. The Motorist is then killed in the lounge with a wrench. Colonel Mustard finds a secret passage that leads back into the lounge and he and Miss Scarlet find The Motorist dead. Yvette grabs the revolver and shoots at the door's lock, letting Miss Scarlet and Colonel Mustard out. The doorbell rings once more and the guests open the door to find The Cop on the other side. He tells them he came to check up on an abandoned car that he saw. He asks to use their phone and they lock him in the library. The phone rings and The Cop answers the phone and tells the guests J. Edgar Hoover is on the phone. The Cop demands to go into the lounge and the study. When he opens the door to the study he finds Mrs. White kissing Mr, Boddy's corpse and Colonel Mustard hugging and kissing The Cook's corpse. He then goes into the lounge and thinking that The Motorist who had a bottle of booze put in his hand is drunk, he tells the guests to make sure The Motorist doesn't drive home. The Cop is locked into the library again and the guests continue their search of the house. Miss Scarlet finds another secret passage that leads to the study. The power is turned off and Yvette is strangled with a rope in the billiards room. The Cop is then killed with a lead pipe in the library. The doorbell rings once more and The Singing Telegram Girl, who is at the front door is shot dead with the revolver. The power is turned back on and the guests return to the entryway. They find Yvette, The Cop and The Singing Telegram Girl dead.
Wadswoth tells the dinner guests that he knows who did it and how they did it. He then runs through the mansion, along with the guests going over the events that happened during the evening, but pointing out instances of people missing from the larger group and also telling them that all of the help were involved in gathering blackmail information for Mr. Boddy. The doorbell rings and when Mrs. Peacock answers it, The Chief is at the front door posing as a religious person handing out pamphlets. Wadsworth then breaks down who murdered who one by one. Professor Plum murdered Mr. Boddy, Mrs. Peacock killed The Cook, Colonel Mustard killed The Motorist, Mrs. White killed Yvette, Miss Scarlet killed The Cop, and he shot The Singing Telegram Girl. Wadsworth reveals that he is really the one that had been blackmailing them and used them to kill his informants. He proposes they leave and he will continue to blackmail them, but suddenly Mr. Green pulls out a gun and shoots Wadsworth dead. Mr. Green then reveals he works for the FBI and they were all under investigation. He opens the door and a group of police including The Chief enter the mansion and put the other dinner guests under arrest.