Shortly after being engulfed by a black void devoid of matter or energy, the Enterprise confronts and destroys what appears to be a Romulan warbird. It turns out that the warbird was merely an illusion created by a space-dwelling entity called Nagilum.
Ensign Haskell - An Enterprise conn officer portrayed by Charles Douglass. In order to understand the concept of "death", Nagilum triggers some kind of cerebral hemmorhage in Haskell. Haskell appears to go into a seizure and collapses dead upon the floor of the bridge.
A peace negotiation on Solais V breaks down when a traitorous Solari combatant attempts to kill the mediator Riva. Riker pulls Riva out of the line of fire but the Solari's laser beam strikes Riva's "chorus", three telepaths that communicate for the deaf and mute Riva. The chorus members are disintegrated and the Solari traitor is killed in the same way by his commander.
The Enterprise recieves a distress signal from Starfleet vessel USS Langtree. When they arrive, they find that the crew are all dead, apparently having all died of old age. It is later discovered that the Federation genetic facility Darwin Station has been contaminated with an affliction that accelerates the aging process.
The USS Yamato - a Galaxy-class ship like the Enterprise-D - picks up an ancient alien program that infects the ship's computer systems like a virus. The alien software triggers a warp core breach that destroys the Yamato, killing its entire crew of over 1000.
After being flung into the distant System J25, the Enterprise discovers an M-class planet that used to support an advanced civilisation, but all of the planet's city structures have been ripped off the surface in the same way as the outposts as in the episode "The Neutral Zone". Minutes later, the Enterprise encounters the beings responsible for all those incidents: the Borg.
A Borg drone beams onto the Enterprise to extract information from its computer banks. Worf tries shooting the drone but its body armour protects it from the stun setting. Worf then sets his phaser to kill and shoots the drone dead. However, another Borg immediately beams over and resumes its fallen comrade's work. Worf tries shooting the new drone but it is protected by a forcefield around its body. After the drone completes its information extraction, it removes several components from the fallen drone's body before returning to its ship. The deceased drone's body then disintegrates.
In a brief battle between the Enterprise and the Borg cube, the Borg drain the Enterprise's shields then use a cutting beam to carve out a portion of the Enterprise's saucer section, extracting it with a tractor beam. Eighteen people were in the dissected portion of the ship and are presumed dead.