After waking up surrounded by dead bodies and no memory, Myfanwy Thomas is thrown into the world of the Checquy, a paranormal secret service where she's a high-level operative known as a Rook - and no one can be trusted.

While Myfanwy revisits the crime in search of her past, Monica discovers a dark truth about one of the victims - her lover and fellow agent. One of Myfanwy's dead attackers disappears from the morgue.

Myfanwy stumbles upon a disconcerting clue regarding her mysterious past; Farrier attempts to find a scapegoat that he can use for the bankside murders; Monica gets ready to do some undercover work as she attends an EVA auction.

Myfanwy uncovers a twisted relationship with her psychiatrist; Monica searches London with Gestalt for a missing EVA who escaped; Farrier makes a connection with a mysterious prisoner.

Myfanwy and Monica work to extricate a young EVA, while Gestalt's suspicions of Myfanwy lead to a confrontation.

While Myfanwy returns to her childhood home, Farrier faces consequences at the Checquy and Monica copes with the discovery that she was betrayed by Marcus.

After a terrifying prophecy, Myfanwy's desperation leads her to a place to trust in a powerful enemy. But when her plans go awry, she is forced to run for her life while her memory slips away.

Myfanwy and Farrier quickly discover how dangerous life is outside of the Checquy, while Grantchester runs out of options. Myfanwy chooses between her freedom and Farrier's life.

The London-set series centers on a young woman pursued by shadowy paranormal adversaries while grappling with extraordinary abilities of her own. After waking in a park with total amnesia surrounded by dead bodies, she must fight to uncover her past, and resume her position at the head of Britain's most secret (supernatural) service before the traitors who stole her memory can finish what they started.

The London-set series centers on a young woman pursued by shadowy paranormal adversaries while grappling with extraordinary abilities of her own. After waking in a park with total amnesia surrounded by dead bodies, she must fight to uncover her past, and resume her position at the head of Britain's most secret (supernatural) service before the traitors who stole her memory can finish what they started.