A man makes his way through the woods to Peter’s house. Inside, Peter is working and Diane advises him to take a break before he tires himself off. He gives in and packs up his papers into a briefcase, unaware that someone is at the window watching him. Once Peter leaves his study and goes to bed, the intruder comes in through the window and goes to the briefcase.
The next day Peter comes downstairs and goes to his study, and discovers that his briefcase is gone. Diane dismisses it as him misplacing it, but Peter doesn’t believe it. They wonder if Sally moved it, but she denies it and points out that the window sill is broken. Diane doesn’t know why a burglar would take the briefcase and nothing else, and Peter warns that without the information, he’ll have to start all over again. He calls in the police and Inspector Quillan determines that someone broke in, but has nothing else to go in .
Lucian Currie calls Peter later and tells him that he found Peter’s briefcase in his garden. Lucian is glad to have Peter come over and get it and provides his address, and Peter drives over on his own since it’s night and no one will see him. The butler, Collins, lets him in and Lucian invites him to sit down and have some coffee. He finally comes to the point and tells Peter that he had Collins steal the briefcase and used it as bait to lure Peter there. When Peter tries to leave, Lucian orders his dog Juno to grab his arm and restrain him. Peter has no choice but to sit down and Lucian points out that Juno can sniff Peter out even if he removes his clothing and bandages. He admits that the dog is dangerous and was ordered to kill it, but he hid it from the police. Lucian finally gets down to business and explains that he and his partner, John Vickers, own a gold mine, and that the survivor inherits the entire mine. However, his partner refuses to die and Lucian tells Peter to kill him because he has no choice. Vickers is coming to see him that night and Peter is to eliminate him.
Vickers and his bodyguard Ryan are coming to Lucian’s manor at the latter’s invitation. Lucian has said that he’s willing to sell for a fair price and let Vickers buy his share of the mine.
Lucian explains that he wants Peter to strike Vickers a single time to the chest. The man has a heart condition and Lucian figures the one blow will dispose of him. When Peter suggests that Lucian wait, Lucian says that he’s been waiting 15 years and there’s no indication that Vickers is going to die. He can’t do it himself because of Ryan, who is always at Vickers’ side. Lucian wants him there because Ryan will have to testify that no one apparently touched his boss when he died of his heart attack. Peter tells Lucian that he’s sick and runs out the door into the next room. He closes the door behind him but Juno circles around and goes to the window. Peter removes his clothing and bandages and slips back into the house, but Lucian calls Juno back. The dog corners Peter and Lucian tells him to go back and wait for Vickers.
Vickers and Ryan pull up and Lucian tells Peter how everything should occur. Collins lets the two men in and escorts them to the study. While Lucian offers to sell his share of the mine, claiming he needs the money. Vickers notices that Juno keeps staring at the chair where Peter is seated. Lucian offers a mere $2 million and Vickers rants at his partner, while Peter makes a run for the door. He gets out and barricades it, and Ryan busts down the door as Peter runs outside. Juno attacks Ryan and runs after Peter, while Lucian takes the bodyguard’s gun and advances on Vickers. Since there are no witnesses, Lucian hits Vickers in the chest and he collapses, seemingly dead. Collins sees the entire thing and Lucian reminds him of the arrangement, and that it will appear that Vickers died of a heart attack. They hear Juno barking and go out to make sure that the dog disposes of Peter.
Juno has chased Peter into the garage. As Lucian and Collins pound on the door, Peter hotwires the car and drives out through the garage door. Lucian tells his butler that they’ll have to flee the country and he has friends who will help, but Collins figures that he can talk his way out of it since he didn’t kill Vickers. He demands his share of the money and promises to keep the police off his track, and Lucian agrees to pay him off.
Peter calls Diane and has her call the police, and then goes back to Lucian’s house. Meanwhile, Lucian takes his money out of the safe and draws his gun on Collins. He tells Juno to stay, telling the dog that he can’t take him along. Lucian then forces Collins out to Ryan’s car and he drives away. Collins grabs the gun but Lucian speeds up and warns that if he dies, the car will go out of control. They’re unaware that Peter has slipped into the car. He shuts the engine off and takes the key. Lucian assumes that Collins took the key, but the butler has no idea what has happened. Peter grabs the gun from Collins and forces Lucian to drive back.
Back at the house, the doctor is called in and confirms that Vickers is alive, thanks to some quick artificial respiration performed by Ryan. Vickers vows to make sure that Lucian is put away and then out live his partner. Peter comes in and gets his briefcase, assuring Quillan that he’s there to get what he wanted. As he leaves, Peter sees Juno, much calmer without his master’s influence. Realizing that the dog has lost his master, Peter invites the dog into his car and drives away.