Timesmith

Thirteen-year-old Jack Morrow is haunted by the past. For Jack is a Timesmith, someone with the ability to travel through Sorrowlines, the channels that connect every gravestone with the date of the person's death. Desperate to help his family, Jack finds himself in a secret world deep under the streets of 1940's London. Hunted by the undead knights of the Paladin, Jack must find the fabled lost sword of Durendal before it can be used to resurrect the Paladin's evil master, Rouland.