With no immediate threat, they inspect the void, and find it looks exactly the same no matter in which direction or how far out they look. When they eventually try to leave, however, they find they don't really seem to be moving anywhere. They try dropping a stationary beacon and heading away from it, but shortly discover they're heading back towards it. As the crew's concern increases, a Romulan ship appears and fires.
The Enterprise destroys it with one torpedo, and are puzzled to detect no debris. Then, their sister ship, the Yamato, appears, but does not respond to hails. Riker and Worf beam over to check it out. While they find a strange, Escher-like joining of bridges, the Enterprise sees an opening, but cannot leave while they away team is on the Yamato, and communications are out. After they let the exit vanish, communications mysteriously come back up, and the away team, jumpy, is beamed back aboard just as the Yamato vanishes. Several similar openings appear, but vanish whenever the ship tries to move towards them. Just as Pulaski remarks that this all feels like a psychology experiment on rats, a mysterious face appears in the void.
It announces itself as "Nagilum", and after asking a few questions, decides it wants to examine the phenomenon of death. It kills one crewman, then says it must learn about "every kind of dying", and expects it will take thirty to fifty percent of the crew. Shortly after this, in a conference, Picard decides that there's only one option: destroy the Enterprise. He and Riker set the auto-destruct, with a twenty minute countdown.
After about fifteen of those minutes have gone by, Picard is visited in his quarters by Data and Troi. After Data asks about death, both tell Picard in no uncertain terms that it is wrong to destroy the Enterprise. Picard says, "yes. This is very wrong. Neither of you should be reacting in this way," and finds out from the computer that Data is on the bridge. Nagilum's simulations vanish, and so does the void. After ordering the ship well clear of where they were, Picard aborts the destruct. Nagilum appears on the screen in Picard's ready room a short time later, to present its conclusions, and expressed its amazement that humans have survived. Picard points out that both species share the trait of curiosity, and Nagilum vanishes, as the Enterprise continues on.
Program highlight
STAR TREK: THE NEXT GENERATION - "Where Silence Has Lease" - The crew is held hostage in a mysterious void by a being who wishes to observe the many ways in which humans die.