“Dance of the Mayflies” is episode fifteen of season two of Andromeda.
The Andromeda Ascendant is trying to evacuate the inhabitants of a drift (a type of space station) that has been attacked. During the process, the attackers return and start attacking the Andromeda too. Oddly, the attackers are the Than, with whom the Andromeda has previously had good relations, so why are they attacking?
Then it turns out that everyone on the drift was infected with something that is killing them, and now Beka has it too. Even worse, when those infected die, this doesn’t seem to slow them down much. Instead, the dead are getting up and trying to take over the ship.
Space going zombies? Who would have thought it.