Doctor Who: White Ghosts (3.2)

A close encounter with a stray missile leads the Doctor to materialise his TARDIS on a planet that hangs in the dark at the edge of the known universe. A planet so dark that it exists in near-permanent night. A planet that enjoys just a single day's light once every thousand years...

Exactly what happens on the planet in its rare daylight hours - that's what a geographical survey headed by Senior Tutor Bengel is stationed here to establish. They, the Doctor and Leela are about to discover that when daylight comes, the White Ghosts rise...

So don't be afraid of the dark. The cover of night is a mercy.