The ship is stranded as crew members fall to waking nightmares.
The Enterprise finds the Brattain, a science ship, with its crew dead or insane, and soon discovers that the ship is trapped in a spatial rift. Soon, the crew of the Enterprise begins to suffer from hallucinations and violent dreams, and they find that they cannot get proper sleep. Only Counselor Troi seems to be dreaming.
The episode is a tense, atmospheric story that has more than a touch of horror. The crew has to understand why sleep is disturbed and what Troi's dreams mean. The answer, when it comes, depends on a delicate act of communication. It is a good example of the series' ability to create unease through ordinary events like exhaustion, and it features a memorable performance by Troi.