The Rook follows Myfanwy Thomas, a woman who wakes up in a London park surrounded by dead bodies with no memory of who she is or how she got there. She soon discovers that she is a high-ranking official in the Checquy, a secret British government agency that protects the country from supernatural threats. As she navigates her new reality, she must contend with her own emerging, dangerous abilities while trying to uncover the conspiracy that led to her memory loss. As Myfanwy attempts to piece together her past, she finds herself caught in a web of betrayal and internal power struggles within the Checquy. With enemies closing in and her own identity in question, she must determine who she can trust—including her own past self—to survive and protect the agency from an existential threat that could destroy everything she has been tasked to defend.