Vampire Plagues: London, 1850 (Book 1)

Plot

An enormous ship has just reached port. From its hull, a flock of bats ascends and disappears into the streets. Jack Harkett intends to board the ship, in search of food or money. Instead, he encounters a boy his own age -- running for his life! The boy recounts horrific tales about a vampire plague that's killed the entire crew. With no one to turn to but each other, the two boys vow to stop these horrors from continuing. Their pledge will take them on dangerous adventures from London to Paris and finally to Mexico, to confront the beast who started all this destruction.