Mysterious troubles on the USS Sisyphus begin when crew members become invisible and then completely intangible, a mystery that deepens when an exact copy of the ship appears alongside them in space. Commanded by Captain Fritz Fassbinder, this alternate Sisyphus has the same crew as the one audiences have come to know and love, but with different positions onboard ship, from Science Officer Winslow Heffington III to ship's barber Julius Baxter. The other ship admits they found themselves in this universe after exploring a strange nebula, and are also having crewman turn invisible and fade away. A party beams over from the Alt.Sisyphus and determines the vanishings are a result of the two ships trying to co-exists, a process that, at least on the Alt.Sisyphus, is exacerbated by Abba songs. The two crews work closely together to find a solution, during which time Dr. "McCloud" merges with his gas cloud doppelganger(a process which appears to be permanent). On Alt.Sisyphus the alternate crew debates whether they should destroy this universes' Sisyphus to keep from fading away, or keep searching for a scientific solution. The merged Dr. "McCloud" makes the case that the most heroic course of action would be to fly into a nearby star, killing themselves and saving their counterparts, an argument that wins over Captain Fassbinder. The Alt.Sisyphus flies into the star(though without Dr. "McCloud") blasting Abba's "Take a Chance on Me." Onboard this universe's Sisyphus, a memorial service is held to honor their sacrifice as crew members slowly reappear. Inspired by the noble sacrifice of their doubles, Captain Baxter orders the ship into a nearby sun. He is presumably talked out of it.
Take a Chance on Me – Abba