Neverwhere

Richard Mayhew (Gary Bakewell) is living in London. One day he happens upon an injured girl named Door (Laura Fraser), and though his fiancee tells him not to help her he does. Now that he has helped her he suddenly becomes aware of a magical realm beneath London referred to as London Below by its inhabitants. The unfortunate side effect of helping Door is that Richard has now ceased to exist in the world of London where he comes from. Now he must make his way through this strange realm and try and figure out how to get back, and he must also help Door survive danger from her enemies.