Ali Dawson is a police detective who leads a unit that investigates cases so cold her team must travel to the distant past to solve them. But Ali and the team haven't been allowed to time-travel ever since their technical expert, Jones, got stuck in Victorian London, never to be seen again.

To distract herself from meaningless tasks, Ali decides to look into a present-day case - a series of apparent suicides, all young men who fell to their death from high places. She believes the deaths are linked to a psychic medium called Barry Power, who convinced the boys they could fly. Ali goes to one of Power's shows where he claims to be in contact with Jones.

When Ali notices that evening that her cat, Terry, has gone missing, she decides to go back in time just long enough to prevent Terry from escaping through his open cat flap. A dangerous plan which backfires, and she finds herself once more in Victorian London, where she meets Jones, as well as Power, and the darkly mysterious Cain Templeton with whom Ali has unfinished business from her previous visit to the past...