Into the Breach (1)

The former crew of the U.S.S. Protostar and now warrant Starfleet officers in training — Dal, Rok-Tak, Zero, Jankom Pog, and Murf — are reunited for an internship under the command of Admiral Janeway. They soon meet The Doctor, a dear friend of Janeway, who escorts them to the admiral's new ship. Starfleet has asked Janeway to observe a new wormhole to deem if it poses a threat — the very wormhole they created when they self-destructed the Protostar.