Richard Mayhew lives in London, has a job, and has a fiancee. One day he stops to help a girl he who is laying on the ground bleeding (despite his fiancee's protests). He takes the girl back to his house.
By involving himself in this strange girls life, Richard suddenly disappears from his own life. He is neither seen, nor heard, by anyone he knows. Richard is forced to search London Below (where the strange girl came from) to find the girl and, hopefully, reappear in his own life. Richard gets caught up in the strange girl's search to learn why her family was murdered and why someone wants the same for her.
There were several well-placed eccentric characters (I feel like sometimes eccentric characters can get annoying in a story), and although the story was very predictable at times, I enjoyed it.