Time and Again

Voyager is hit by a shock wave and finds that a nearby inhabited planet has been devastated by a polaric energy explosion. On an away mission to the ruins, Janeway and Paris fall through a temporal fracture and arrive on the planet a day before the disaster. Trying to avoid interfering, they are caught up with a group of saboteurs targeting the polaric power plant, who see their Starfleet equipment, take them for infiltrators and force them to take part. Back aboard Voyager, Kes senses what is happening through her emerging psychic abilities, and the crew work to open a rift to bring the pair home. Janeway then realises that the rescue attempt itself will trigger the explosion. She closes the rift with her phaser, preventing the catastrophe and changing history. In the restored timeline, Voyager detects the planet with its pre-warp civilisation intact and, respecting the Prime Directive, continues on its way without making contact.