The Enterprise enters an uncharted binary star system in search of a science vessel, the U.S.S. Brittain, which has been missing for about a month. It finds the Brittain, intact but adrift...and all the crew are dead of extremely unnatural causes.

All but one, that is. The scientific advisor, Hagan, a Betazoid, is alive, although catatonic and withdrawn. While Troi tries to get through to him, Geordi and Data try to restart the Brittain's engines-but although everything's working fine, there's no motion. Before long, Beverly tells Jean-Luc of her findings-the crew of the Brittain, with no apparent outside influences, killed each other. Meanwhile, Troi has a nightmare, of floating adrift in a fog with a voice saying only "eyes in the dark, one moon circles..."

Four days later, with no answers in sight, and tempers mounting (O'Brien gets paranoid about Keiko's alleged "affair" with another man, for example, and Picard hears his ready room door buzz many times with no one there), Picard decides to leave the area. Unfortunately, the engines suddenly fizzle out and stop working, leaving the ship adrift. Data's analysis (six days later...) shows that they're caught in a "Tychon rift", and need a large explosion (greater than even the photon torpedoes can generate) to break free.

Picard, realizing that one of the two top officers needs to keep hold of his sanity, sends Riker off to a nap. Unfortunately, neither one gets any rest: Picard hallucinates in the lift and comes to the bridge screaming like a baby, and Riker feels snakes on his leg moments after getting into bed. After a brief conversation with Data in which Data suggests the deflector burst (a\*` la "The Best of Both Worlds") as a possibility, Picard tells Data that he'll need to help Picard out more and more as this continues.

After Bev has a brief hallucination, she figures out what's wrong: except for Troi, no one has had any dreams since this began, and the dream- deprivation is driving them all slowly insane. As unrest builds in Ten-Forward (with a crewman, Gillespie, deciding he'd rather go down fighting than quietly in his room), the deflector burst is tried, and fails miserably. After this, Worf, feeling that his fear makes him no longer a warrior, tries to commit suicide, but Troi stops him and takes him to sickbay.

Finally, after Data's been appointed Acting Captain, Troi figures out that her nightmares are not dreams, but messages. There's another ship on the other side of the rift, and its beings are trying to communicate telepathically on Troi's mental frequency (thus jamming out all humanoid REM frequencies at the same time). After some study and a bit of good fortune, Troi and Data realize that the other crew needs hydrogen from the Enterprise in order to create the necessary explosion. As Data does this, Troi communicates to the aliens that they should release the catalyst, and both ships are freed.