S4E17 · Night Terrors

The Enterprise is searching a binary star system in an effort to find the USS Brittain, a Federation science vessel which went missing a month earlier. The crew locates the ship but the Brittain is derelict, and all the crew are dead save one: the ship's Betazoid science adviser, Andrus Hagan, who is discovered hiding in a room just off the bridge. Hagan has somehow survived, but he has been shaken by the experience and is in a profound catatonic state. Counselor Deanna Troi tries to use her telepathy to contact Hagan.

Meanwhile, Geordi La Forge and Data set to work repairing the Brittain but discover that although everything is in working order, the ship still fails to move. Dr. Beverly Crusher determines that all of the Brittain ' s crew died at each other's hands. That night onward, Troi has trouble sleeping, encountering the same dream in which she levitates and drifts in the direction of a mysterious voice repeating, "Eyes in the dark, one moon circles".

Four days later, with the investigation stalled, Captain Picard decides that the time has come to move on, but the crew find the ship also stalled like the Brittain. Data discovers that both ships are trapped in a spatial phenomenon known as a "Tyken's Rift", and they can only escape through the force of a tremendous explosion. However, as they work at determining how to create this explosion, the crew starts becoming irritable and experiences hallucinations. Dr. Crusher realizes that everyone but Troi has failed to achieve R.E.M. sleep since entering the rift, leading to their current state. As violence begins to erupt around the ship, Picard assigns Data, who does not sleep or dream and is therefore unaffected, as acting Captain.

Data eventually attempts to use a pulse from the deflector aimed at the center of the rift to create the explosion, but this fails to produce any effect. Meanwhile, as Troi listens to Hagen, she hears him mention "eyes in the dark" and realizes that he has been having the same dream she has. This leads her to realize that it is not a dream, but a message. As Data looks for other solutions with Troi, they realize that "eyes in the dark" may refer to the nearby binary star system, and "one moon circling" may be a description of a hydrogen atom.

Data and Troi work out that there must be another ship from a psychic race trapped on the other side of the rift who is aware of their presence but looking for hydrogen to create an explosion. Troi goes to sleep to contact the other species through the dream, while Data vents hydrogen into the rift. An explosion soon occurs, and both the Enterprise and the alien ship are freed. As the crew recovers, Data returns the ship to Picard, but not before ordering everyone to get some sleep.