Parallel universe (False Negative)
From Tardis Wiki, the free Doctor Who reference
In the 2010s, N-Space UNIT personnel discovered a travel capsule which brought them into contact with a parallel universe containing "evil" versions of themselves. This reality's Kate Stewart knew the Doctor as a man who roamed the universe to annihilate "pathetic, pacifist aliens". (AUDIO: False Negative [+]Loading...["False Negative (audio story)"])