Returning to Syndicate 9 after a year with Vice, Rachel needs some time to rekindle her neglected friendship with Janet, but the shocking murder of Michael Edgerton forces her to hit the ground running as she steps up to Acting DI under the watchful eye of Julie Dodson. When a teenage boy sees a clip of Michael's murder on the darknet, it's clear that Syndicate 9 are dealing with something much bigger and more sinister than a single, indiscriminate murder. A sick game is being played and Syndicate 9 need to find the next potential victim before the killer does.

Glad of Rachel's return, Janet couldn't have known how much she was going to need her friend. When Taisie is arrested, setting off an inconceivable chain of events, Janet is thrown into turmoil and Rachel's wisdom and experience are exactly what she needs to steer her through the crisis.

Rachel is criticised for the lack of progress in the investigation and with Steve Dench still the prime suspect, she knows she must find both a murder weapon and the encryption code used to access the Taking Out The Trash website. Then, they not only get Steve for multiple murders, but they also find the man he's playing his sick game with. Discovering that the witness at Michael Edgerton's murder may be one of the killers marks a big breakthrough, and with the attacks increasing, Rachel hopes that the killers will start to make mistakes. The appearance of a star on Rachel's gatepost terrifies Alison and when Julie Dodson finds out, Rachel's position as Acting DI is jeopardized. But with new evidence challenging Steve's alibi and a positive ID of the witness, Rachel is determined to hang onto the case. When Janet's attempt to help Taisie results in a complaint, her faith in doing everything by the book is rocked, and with Rachel's pregnancy out in the open, both Scott and Bailey have life-changing decisions to make about their futures.