Murder by Natural Causes

The successful mentalist Arthur Sinclair chats on the phone with his much younger wife Allison, who is secretly in bed with Gil Weston. Allison and Gil are already plotting to kill Arthur by frightening his heart to death. Arthur departs for a television interview, unaware of the conspiracy brewing back home.

Allison explains the plan to Gil Weston: he will storm the house pretending to be a burglar and then point a pistol at Arthur to cause a fatal heart attack from the shock. The scheme hinges on a clean, unexpected confrontation that looks like a crime of passion. They anticipate Arthur will be overwhelmed and die as planned.

Gil Weston breaks into the house and pretends to be a journalist there for an interview with Arthur. He and Arthur quickly discover they know each other’s secrets, establishing a tense, cat-and-mouse dynamic. The ruse is meant to extend the staged encounter and keep Arthur off guard.

Gil uses Arthur's competitive spirit to push him into performing 50 push-ups, hoping to tire his heart and make the staged plan more convincing. The two men trade barbed remarks while the physical exertion raises the stakes of the encounter. The tension builds toward a violent outcome.

Gil draws the gun and a struggle ensues between him and Arthur. In the ensuing melee, it seems Arthur shoots Gil, seemingly securing the success of the plot. Allison returns home unaware of the immediate aftermath, adding to the growing suspense.

When Allison enters, she finds Arthur distraught but discovers that Gil is alive behind Arthur, having loaded a blank into the gun. Arthur stumbles in pain but then laughs and applauds as the two lovers look on, indicating he has known about their affair all along. The ploy has not gone as planned, and Arthur reveals his own counterplay.

Arthur declares that he has known about Allison and Gil for months and is now prepared to turn the tables on them. He demonstrates that he has been orchestrating a longer game, using their plan to reveal their betrayal. The balance of power shifts in his favor as he moves to outmaneuver them.

George, Arthur's lawyer and longtime friend who is also Allison's real lover, arrives and shoots Arthur. He and Allison depart, leaving Arthur's fate uncertain and the apartment filled with troubling questions about loyalty and deceit.

Some time later, Allison returns to the house and finds that Arthur's body is missing. The disappearance hints that Arthur anticipated the murder attempt and staged a deception to keep his life intact while continuing his mind games.

It is revealed that Arthur had replaced all the bullets in the gun with blanks, a calculated move to survive and to keep manipulating the situation. This twist confirms that his long game was about control as much as about revenge.

In the final moment, Arthur points his pistol at Allison, now loaded with real bullets, and asks her to read his mind. The line signals that the mentalist remains several steps ahead and that the ultimate weapon in his game is psychological maneuvering rather than physical force.