Police detectives rely on Amy Lane to track the digital debris of their most elusive criminals - when she's not in the throes of a panic attack.

After two students disappear in Cardiff, Amy uncovers photographic evidence that they've been murdered. From the safety of her computer, she looks through the city's digital eyes to trace the steps of a killer.

Amy's investigation requires footwork, however, and the agoraphobic genius can't hack it alone. She turns to her newly hired cleaner, ex-con Jason Carr. Jason is fascinated by both Amy and the work and can't refuse even when she sends him into situations that risk returning him to prison.

The killer strikes again and again, and Amy and Jason are the only investigators closing in on him. But Amy's psyche is cracking under the strain, and Jason's past is catching up with him. To stop the next murder, they must hold their unconventional partnership together at any cost.