There`s something going bump on the Metropolitan line and Sergeant Jaget Kumar knows exactly who to call. It`s PC Peter Grant`s speciality . . . Only it`s more than going `bump`. Traumatised travellers have been reporting strange encounters on their morning commute, with strangely dressed people trying to deliver an urgent message. Stranger still, despite calling the police themselves, within a few minutes the commuters have already forgotten the encounter - making the follow up interviews rather difficult. So with a little help from Abigail and Toby the ghost hunting dog, Peter and Jaget are heading out on a ghost hunting expedition. Because finding the ghost and deciphering their urgent message might just be a matter of life and death.