Sorry for the delay, I usually post this on Thursdays but I've been on vacation for the last week and half or so and have been... lazy. Anyway, I wanted to get on a "more normal" schedule of posting these closer to the start of the week rather than the end.
This is one of those episodes that seems like is hated or shrugged at more than it's liked. It's got it's corner moments (mostly the ones inside Troi's dreams) but overall I think it's a very good episode.
The Enterprise is investigating the loss of a Federation ship and they find it in an unexplored area of space, the entire crew dead. Investigations show that the crew likely killed themselves or one another save for one, a catatonic Betazoid.
The ship sticks around to investigate and as time goes on members of the Enterprise find themselves growing more and more unsettled and seeing and experiencing strange manifestations. Meanwhile Troi has been having strange, vivid dreams and has been trying to telepathically communicate with the catatonic Betazoid who only repeatedly thinks the same cryptic thoughts that don't seem to mean anything.
Before too long the crew discovers that the ship is mysteriously trapped in a space phenomenon they siphons energy from whatever is in it. Whenever the ship tries to move the rift absorbs the energy, preventing the ship from moving. But this phenomenon doesn't explain the strange behaviors growing among the crew.
Beverly soon discovers that the crew's behavior is due to a lack of REM sleep, the crew isn't dreaming. The lack of dreaming has prevented the brains of the crew from organizing thoughts and doing what needs to be done during REM sleep causing the paranoia and lack of clear thoughts from everyone. Even the non-human crew members are being effected (save Data), except for Troi who is only having the same nightmare causing her to avoid sleep.
Eventually they come to the conclusion that Troi's sleep disturbances are coming from another ship trapped in the rift that's trying to communicate with Troi in order hatch an escape plan for both vessels. They were trying to do this with the Betazoid crewman from the other ship but he went catatonic before a solution could be hatched.
Data and Troi surmise that the aliens are asking for the Enterprise to release hydrogen gas into the rift as a catalyst for a reaction with another element/chemical the alien ship has. Troi is able to deliver the message to the aliens to cause the reaction, freeing both ships from the rift.
Once free, Data, temporarily in command, orders Picard to bed.
There's a lot of good eerie moments in this episode in how it handles the unsettling hallucinations the members of the crew are having. It's also a pretty good episode for Troi as she works to solve the problem.
Overall, I think this episode tends to be underrated and is really a good, eerie, episode. I remember watching it once with a friend, a neurology student in college, who really enjoyed the neurological aspects presented in it concerning REM sleep.
I thought Sirtis did a good job in the episode.
