Detective Chief Inspector Kate Simms is in the United States on sabbatical with St Louis PD. She is working with a 'method swap' team, reviewing cold cases, sharing expertise. Forensic expert Professor Nick Fennimore also happens to be in the States on a book tour and is engineering his trip to get down to St Louis--the last thing Simms wants . . . But a call for help from a sheriff's deputy in Oklahoma distracts the professor: a mother dead, her child gone. Fennimore's quick mind rapidly gets to work, and gradually draws the conclusion this might not an isolated case. How many other young mothers have been killed, their murders unsolved, their children unaccounted for - and what of Simms' cold case in St Louis for instance?