A void in space seems to drift into the path of the ship.
The Enterprise is drawn into a strange void in space, where the ship seems to be cut off from the rest of the universe. A powerful being named Nagilum appears and claims to be conducting an experiment on the crew to understand death, which it does not comprehend, killing some of them to study their reaction.
Picard, left with few options, chooses to put the question to the test by threatening to destroy the ship. The episode is a tense, philosophical story about what it means to be mortal and how a being can study life without grasping it. The result is a thoughtful, spooky and memorable second-season entry, and a reminder of how far the crew will go to protect its freedom.