When Royal Air Force pilot Lt. Kate Sinclair is shot down over Afghanistan, she finds refuge in an abandoned underground bunker where deadly man-made biological weapons - half human, half alien - are awakened.

Hellboy comes to England, where he must defeat Nimue, Merlin's consort and the Blood Queen. But their battle will bring about the end of the world, a fate he desperately tries to turn away.

A man struggling with his faith is haunted by the sins of his past but is suddenly thrust into the role of defending humanity from the gathering forces of darkness.