Torchwood, Series 4: Miracle Day

[On an alien encountered during a past adventure]

Jack:
It's a parasite. Like a bug.

Angelo:
A parasite? Tell me more about it.

Jack:
Good man. It's a species of brainspawn treated as vermin on more than 150 planets that I know and valued as dinner on one other. It tastes like oysters.

Angelo:
You did not.

Jack:
I had to be polite. Now this part drills into the brain of the host and deposits its larvae there. Little worms, sharp as needles, pushing into the brain very slowly. You go insane, but it takes years. Franklin Roosevelt, he's going to be elected Governor of New York this November. But he wouldn't start making the really crazy decisions until his second term as President. Result, America destabilises, pulls out of the war, Germany rises, the Third Reich triumphant and there's a whole new history sprawling out.

Angelo:
You mean someone is changing the future?

Jack:
Destroying it. Turning order into chaos and feeding off the results.

Angelo:
Who would do such a thing? These people above Maranzano?

Jack:
They're just being used by someone called the Trickster's Brigade. Believe me, you don't want to meet them.

Angelo:
What sort of men are they?

Jack:
They're not men at all. They're not even human.