DCS Kat Frank returns to work at the Future Policing Unit after a tragic loss, only to find herself thrust into a new high-profile case. On the night of Halloween, a local MP is found murdered, her body put on prominent display in Kat’s hometown with a message that seems meant for her specifically. The victim’s anti-AI sentiments suggest a political motive, and as Kat investigates with her partner AIDE Lock – the world’s first AI detective – she finds herself once again battling her own prejudices about the technological future he represents.

But when the case takes an unexpected turn, the pair are catapulted into a situation far beyond their control, facing down a threat of both national and international significance, and cut off from the rest of their team. Tangled in a web of suspicion and deception, Kat must choose who and what to believe when the truth seems to defy both instinct and logic. Can she set aside her old doubts and put her faith in her AI partner one last time? Or will this case send Lock down a path she just can’t follow – a path that will leave humanity behind for good?