When the Galaxy-class starship U.S.S. Yamato NCC-71807 self-destructs in the Neutral Zone, the Enterprise is sent to investigate. The probe of abandoned planet Iconia infects the Enterprise computer, Data, and that of a Romulan ship with a disabling electronic "virus."

Thalmus Rasulala (Capt. Donald Varley)
Carolyn Seymour (Subcommander Taris)
Dana Sparks (Tactical Officer)

Colm Meaney (Chief Miles O'Brien)
Folkert Schmidt (Doctor)

• This is the first episode Picard orders "Tea, Earl Grey, hot" from the replicator.
  
• The Yamato is a Galaxy-class Starship, the same class as the Enterprise-D.
  
• A representation of the Yamato was created by the creature Nagilum in "Where Silence Has Lease", however the registry number was NCC-1305-E. (It was likely changed to NCC-71807 for consistency purposes.)