As they try to find their way back to known Federation Space, Voyager encounters a quantum singularity — a star that has collapsed in upon itself thereby creating a powerful energy field that surrounds it. They believe another ship to be in jeopardy, and begin the task of saving it from destruction. After several unsuccessful attempts, Captain Janeway and B'Elanna Torres discover that it isn't another ship caught in the distortion, it is just a mirror-image of Voyager. They must find the rip in the singularity that they entered through and pass out of it before it collapses, forever trapping them. Because of her efforts in helping the save the ship, B'Elanna Torres is promoted to Chief of Engineering.

Kate Mulgrew (Captain Kathryn Janeway)
Robert Beltran (Commander Chakotay)
Roxann Biggs-Dawson (Lt. B'Elanna Torres)
Jennifer Lien (Kes)
Robert Duncan McNeill (Lt. Tom Paris)
Robert Picardo (The Doctor)
Ethan Phillips (Neelix)
Tim Russ (Lt. Commander Tuvok)
Garrett Wang (Ensign Harry Kim)

Josh Clark (Lt. Joseph Carey)
Martha Hackett (Ensign Seska)
Justin Williams (Ensign Jarvin)

• B'Elanna beats out Lt. Carey for the Chief Engineer position, even though he was the acting Chief Engineer. She also receives a field promotion to Lieutenant. (The Chief Engineer was killed when the Caretaker brought Voyager to the Delta Quadrant.)
  
• This is Seska's first appearance, and the only time she wears a blue sciences division uniform instead of the gold uniform.