Cybermen

The story you remember is probably...

The Tenth Planet (1966).

Landing in the Arctic, the Doctor discovers that Earth is under attack from its evil twin planet Mondas.

As Mondas drains the life from Earth, the Mondasians invade the Arctic base - and the Doctor meets the inhabitants of Mondas, the Cybermen, for the first time.

Find out more in the The Tenth Planet episode guide.