Chakotay and Tuvok return from a trip, but Chakotay is badly hurt after an electric current swept through the shuttle. In fact his brain has been stripped of all its energy leaving him brain-dead. Kathryn decides to go to the nebula that apparently shot out this electric current at the shuttle. The closer they get the weirder the crew gets, as something seems to be taken over their action for short periods of time. Paranoia sets in - who can you trust?
Wonderful episode and a great example of a rather small story based on even smaller idea that in execution becomes something much more. The whole episode is on board Voyager, and though scriptwriters ones more use unusual life forms and nebula as their canvas it works here. We are kept in the dark as to what is happening until the last moment. I remember when I saw this episode first that it had me totally puzzled. That is great when ongoing series like Star Trek, with their somewhat conventional story telling, can bring you an episode that keeps you wondering until the end.
What is also fun here that we almost have an Alfred Hitchcock paranoia moments here. The crew finds out that an entity is taking over people's mind, they get paranoid, seeing strange behaviors as a clear sing of someone being 'possessed'. This also makes commanding the ship extremely difficult, making Kathryn for the first (but not last) time transfer all command codes to the Doctor. I enjoyed this episode. The only sort of negative is that once you have seen it ones, it doesn't really hold the same magic for the second viewing. It really needs that twist at the end to be exciting. In order for me to give more than 8 for an episode I have to want to see it again soon.