When the Enterprise-D opens communications with the research vessel SS Tsiolkovsky, they hear a message indicating that the crew have gone mad. When they rendezvous, the science ship's crew of 80 are all dead: the bridge crew have been blown out into space after opening an emergency airlock, all other crew members are frozen to death due to shutting down environmental systems.
Lt. Yar fights to the death with Yareena, the First One to Lutan, a politician on Ligon. During the fight, Yareena's poison-tipped gauntlet slips from her arm and strikes a spectator, killing him in a split second.
Junior Lieutenant Singh - Portrayed by Kavi Raz. He is working in the Enterprise's engineering bay when the sentient, non-corporeal Beta Renner entity passes through his work terminal and electrocutes him.
Arthur Malencon - Portrayed by Mario Ruccuzzo. Malencon was a hydraulics specialist during the terraforming project on Velara III. He was killed by a malfunctioning laser drill. It is later revealed that the laser did not malfunction but was seized by a newly discovered "microbrain" life-form that had declared war against humanity.
A robotic drone attempts to gather information from Riker by projecting an image of missing Starfleet captain Paul Rice. When Riker realises he's being played, the drone reveals itself and encases Riker in a stasis field. Data then destroys the drone with his phaser.
Another robotic drone attacks the away team, this one being able to anticipate attacks. Tasha fires at the drone and it evades her phaser beam only to fly into Data's line of fire.
A third robot appears, more advanced than the previous two. This one is equipped with a deflector shield. Riker, Data and Tasha are able to destroy it by concentrating their phaser fire.
Around the end of the episode, the Enterprise manages to destroy a weapons drone that harassed it throughout the episode.
The Enterprise attempts to rescue the crew of an old Ornaran freighter caught in the gravitational pull of a planet. Four of the six crew are saved, the other two perishing aboard their disentegrating ship. They could all have been saved had the crew not beamed over their cargo to the Enterprise first.
In the Enterprise's observation lounge, Captain Picard informs his crew that two Starfleet outposts in the Neutral Zone have been destroyed. The Romulans are suspected as being responsible.
As the Enterprise come closer to the Neutral Zone, they fail to contact any of the nine colonies and bases located in their path. The crew assumes that all of the bases have been destroyed.
When the Enterprise arrives at the Neutral Zone, they discover that Starfleet's Delta 05 outpost has been destroyed. Supposedly, the outpost was ripped off the face of the planet by an unknown force.
The Enterprise arrives at the planet Tarod IX to find that the colony there has been destroyed in the same identical pattern as the other outposts: all structures, machinery and people simply snatched up, leaving no trace.
Romulan Commander Tebok reveals that the Romulans have also lost outposts along the Neutral Zone, destroyed by the same unknown force. It is not until the episode Q Who? that the Enterprise crew discover the force responsible for these atrocities.