Voyager discovers a planet that was the site of a major ecological disaster and receives an automated message from a group of people who went into artificial hibernation nineteen years ago. The message indicates that they were to awaken four years ago, which concerns the crew. The planet is now capable of sustaining life, so Janeway decides to wake the aliens. Once the stasis chambers are beamed aboard, it is revealed that two of the people died of apparent heart attacks and the brains of the other three are interconnected via a computer designed to keep their brains active during hibernation. However, the system has been designed to allow participants to decide whether to wake up and simply deactivating the computer program would kill them. As the aliens should have woken up four years ago, B'Elanna Torres and Harry Kim enter the stasis system to contact the aliens and find out what happened.
Harry and B'Elanna find an abstract environment filled with lively circus characters. They try to talk to a clown who seems to be the leader, but as the clown insists, "Why talk when we can dance?" The party-like atmosphere disappears, however, when Harry and B'Elanna are led to a pink guillotine. Once they realize what is happening, they try to resist, much to the characters' amusement, and Harry is placed in the guillotine. The aliens emerge and Harry is released when the clown realizes that killing Harry will result in Harry and B'Elanna's crewmates terminating the program.
The aliens explain that the computer creates characters based on input from participants' brains; the malevolent clown is an unintended manifestation of fear. Because the computer controls participants' nerve functions, unmanageable stress caused by fear of losing one's head can cause a heart attack. Additionally, the clown can read their minds (although there is a slight delay in order to process the data). He allows B'Elanna to leave in order to contact her crewmates but declares Harry his "new best friend" because he is certain Janeway would not kill Harry by terminating the program.
The clown decides to torture Harry instead, tormenting him with an old fear of hospitals. This fear was caused by a younger Harry becoming involved in a plague situation and witnessing a young woman dying. The clown raises a scapel as Harry's fear reaches a climax, when suddenly The Doctor arrives, calming the situation. The clown is disconcerted by his inability to read the Doctor's mind and learns this was the intent, as Janeway did not want to give the entity any more hostages. He offers the clown a simulated brain if the clown will release the hostages, but the clown senses that Harry and the aliens know an artificial brain would not be the same as real one. However, the alien who created the system gives the Doctor a hint that allows B'Elanna to begin dismantling it. While she does this, the Doctor returns to distract the clown.
The plan works and the characters in the program begin disappearing. When the clown realizes what is happening, however, he swiftly executes the alien who enabled the crew to dismantle his system. He is about to execute a second alien when Janeway realizes he has won and orders B'Elanna to stop. The clown triumphantly declares victory and celebrates. The Doctor enters one final time and informs him that Janeway has offered to be in the system if the clown releases the other hostages.
At first, the clown is highly entertained by the idea of someone "choosing" to be with him. However, once the others are gone, Janeway informs him that she too is a hologram and the real Janeway is not in stasis, connected only just enough to allow the system to be fooled. He realizes this is true once the delay catches up and he processes her thoughts. Janeway tells him that fear exists to be defeated, and as they talk, the lights gradually dim. The clown says "I'm afraid," to which Janeway whispers, "I know," before the clown's last word: "Drat."