The central character is Ali Dawson, a single mum working in the police in London, who has joined a cold case team. However the crimes they investigate are so old, they're frozen - or so their inside joke goes. 

Ali has been instructed, in her latest assignment, to travel back to 1850s London where she is tasked with clearing the name of Cain Templeton, reputed to be part of a sinister group called The Collectors. Cain is the great-grandfather of MP Isaac Templeton who knows of the top secret team and has made the request.

Ali is meant to spend only a couple of hours on the investigation but she's unable to make her way back and is left stuck in Victorian times. Meanwhile her son Finn is under suspicion for a crime back home, in the present day. 

It's a great read - mainly because we are lured into the lives of the characters straightaway. There's humour as well as thoughtful comments about our perceptions of time, and there are great details about life in Victorian times. Looking forward to book two already!