Three 20th century humans are found cryogenically frozen and are revived as the Enterprise heads to investigate the Romulan's sudden appearance in the Neutral Zone.

Marc Alaimo (Commander Tebok)
Anthony James (Sub-Commander Thei)
Leon Rippy (L.Q. "Sonny" Clemons)
Peter Mark Richman (Ralph Offenhouse)
Gracie Harrison (Clare Raymond)

• According to this episode, the Romulans haven't been heard from since the "Tomed Incident". However, in "Angel One", the Enterprise travels to an outpost to defend against a Romulan attack. In "Heart of Glory", they investigate a battle supposedly involving Romulans and Klingons.
  
• This is the first appearance of the new Romulan warbird, later named as the D'deridex-class Warbird. It was designed by Andrew Probert.
  
• Although not actually seen in this episode, the Borg (Season 2, Episode 42 "Q Who") are later said to have caused the destruction of the Federation and Romulan outposts. The Borg were originally to appear in this episode, but due to the Writer's Guild strike, they were removed and did not debut until "Q Who".
  
• Marc Alaimo (Tebok) went on to play Gul Dukat, a recurring Cardassian on DS9.
  
• Data tells us that the year in our calendar is 2364.
  
• The image of Tommy Raymond is associate producer Peter Lauritson.