“For Whom the Bell Tolls” is episode eight of season three of Andromeda.
The Andromeda Ascendant has helped a colony escape from a solar flare. When Beka and Harper are picked up by Dylan on the Eureka Maru, they have a hitch-hiker – a maggot that eats metal.
Said maggot gets on to the Andromeda, and starts breeding and eating and breeding – which isn’t good. Space, spaceships made of metal and creatures that eat said metal do not mix very well – for anything other than the creature that is.
Whilst Harper is repairing things, he sees what he says is a ghost. Thinking he has been spooked by a horror story he was reading, it’s suggested that what he saw was a new crew member. Until Trance sees it too.
The ghost is actually a very old crew member, and causes havoc with the ship’s systems at a time when they really don’t need it.