Businessman Bradley Meredith returns to his office after a six-week vacation and his secretary Mrs. Flannagan greets him. She gives him his correspondence, including a letter with no signature or return address. It merely tells Bradley to read the newspaper and read a particular column that will be of interest to him. Mrs. Flannagan gives him the newspaper and Bradley sees an article about the mysterious death of a go-go dancer, Marilou Doubleday. Bradley abruptly dismisses his secretary.
Later at his club, Bradley finds a letter in his jacket pocket. It says that there are full instructions in the glove compartment of his car. Bradley gets in and his wife Estelle runs up and says that she'll need to use his car because hers is at the garage. He angrily tells her to take a cab and drives off. Down the street, Bradley parks and checks the glove compartment. Inside is another envelope, with a photo of Marilou and a hand-drawn map telling him to be there by 11. There are also instructions for Bradley to bring money. A police officer comes by and asks to see Bradley's driver license, pointing out that he went through a stop sign and writing him a ticket.
That night, Bradley follows the directions out into the country and makes sure the gun in his briefcase of money is loaded. He drives to meet the deadline and runs into a downed telephone pole. Bradley is forced to continue on foot with 15 minutes left. He reaches a farm and the dogs bark at him from behind a wire fence. The businessman pounds on the front door but gets no answer, and discovers that the door is unlocked. Bradley goes inside and finds no one around. He does find a phone in the study but the line is dead.
When Bradley turns to go, he comes face-to-face with an old man. Bradley apologizes for coming in and says that he had an automobile accident, and the old man confirms that the telephone is out. He says that he'll have to ask Sonny to use the family tractor, and right now Sonny is at the theater and Bradley will have to wait until his grandson gets back. Bradley insists that it's a matter of life or death, but the old man refuses and offers Bradley some applejack. The old man walks out of the study... and locks the door behind him, trapping Bradley. On the nearby table are several photos of Marilou, all of them with the face cut out. One of them matches the photo that Bradley received earlier.
Bradley gets his gun out and the old man comes in with a shotgun and tells him to drop it. Once Bradley does, the old man, Doubleday, explains that Marilou was his granddaughter, Sonny's sister. Doubleday admits that Sonny thought up the entire plan and he's mean and clever, and he rigged the telephone pole. Bradley offers him the money, $10,000, and Doubleday says that what Sonny wants, he usually gets, and he doesn't want the money.
The old man says that Bradley's car could sit there for weeks on the road and no one would notice. He then unloads the gun, keeps one bullet, and tosses the clip outside. Doubleday says that they didn't know if Bradley was the one they wanted. They sent copies of the same letter to all eight men in Marilou's diary and Bradley was the only one who came.
Bradley picks up the unloaded gun and then runs to the front door. He wraps his arm in a tablecloth and picks up a discarded baseball bat, and then runs out. The dogs come after him while inside the house, Doubleday plays his guitar and drinks.
Running around the house, Bradley finds the discarded clips and grabs it. He loads the gun and fires, but the dogs jump him and he's forced to run back inside. Doubleday hears the shots but just smiles and keeps playing. He calls out that he figures Bradley has one shot left and warns that Sonny is coming. Bradley tries to find another way out of the house and comes across a coffin with his name on it, labeled "Murderer." He yells at Doubleday, saying that he didn't mean to murder Marilou, and explains that she threatened to tell Estelle they were having an affair. Doubleday tells him that there's another way out but Sonny wouldn't want him to say what it is.
Bradley finally locates a secret passage behind the fireplace and enters the tunnel beyond. Doubleday continues taunting him, saying that he can hear a car coming. Bradley comes to a mirror and instinctively shoots it, and Doubleday calls out that he used his last bullet. The car pulls up outside, and Bradley keeps searching for the other way out. He finds a trapdoor and opens it, and climbs down the rope ladder leading down. It breaks and Bradley falls, breaking his leg.
Doubleday steps into the hallway above with Sonny: a ten-year-old boy. The old man says that they're going to Disneyland, but they'll be back in a month. When Bradley yells that there is no other way out, Doubleday insists that he told him the truth. He tosses down the one bullet he kept and says that it's the other way out. Sonny says goodbye to Bradley as Doubleday closes the trapdoor.