Timesmith Chronicles Series by Niel Bushnell

Twelve-year-old Jack Morrow is used to life being complicated. His mother died five years ago, and his father is now headed for prison. But then Jack discovers he's a Yard Boy - someone with the ability to travel through Sorrowlines, the channels that connect every gravestone with the date of the person's death - and he is quickly pulled into an adventure beyond anything he could have possibly imagined... moreTwelve-year-old Jack Morrow is used to life being complicated. His mother died five years ago, and his father is now headed for prison. But then Jack discovers he's a Yard Boy - someone with the ability to travel through Sorrowlines, the channels that connect every gravestone with the date of the person's death - and he is quickly pulled into an adventure beyond anything he could have possibly imagined.Finding himself in 1940s war-torn London, with his then-teenage grandfather, Davey, Jack soon realises that his arrival in the past has not gone unnoticed. The evil forces of a secret world are determined to find him - and to find out all he knows.As Jack struggles to survive, he comes ever closer to unlocking the dark secret at the heart of his family, and to - just maybe - changing his own destiny... less

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... moreThirteen -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.Separated from his friends Jack is forced into an uneasy alliance with Hilda, a strange girl with a hidden past. Together they must find their way through the treacherous underground city of Ealdwyc and stop Rouland's return. Jack's future, and that of his entire family depends on it. less