Who DS Locke is
Detective Superintendent Locke is the contemporary police officer who repeatedly encounters Susan Ryeland when her reading leads her into a criminal investigation. He has the legal authority, access to official evidence and responsibility for the case. Susan has a close knowledge of Alan Conway’s books and a habit of asking questions that the accepted account does not answer.
The friction between them is more than a running joke about an amateur annoying a policeman. Locke needs evidence that can support police action; Susan begins with literary connections that can sound fanciful. Their disagreement asks when professional certainty becomes an obstacle and when an outsider’s intuition is worth the trouble of testing.
Role in Magpie and Moonflower Murders
In Magpie, Locke investigates Alan Conway’s death. A letter changes the apparent explanation from an accident to suicide, but Susan is troubled by the missing conclusion of Alan’s final novel. Her professional problem and his police case are connected in ways neither initially understands. Locke is understandably resistant to treating a manuscript as a guide to events outside it.
Moonflower brings them together again at Branlow Hall. Locke investigated the killing of Frank Parris and now handles Cecily MacNeil’s disappearance. Susan’s interest in an old Conway novel challenges not only his current decisions but the security of the earlier conviction. Stefan Leonida has already been punished; reopening the reasoning means asking whether an apparently completed case was built on an incomplete picture.
His rank is Detective Superintendent: the television dialogue introduces him in those terms. His title belongs to the contemporary police hierarchy, distinct from the Detective Inspector rank of Chubb inside Conway’s fiction. The shared performer makes the connection obvious, but the two roles remain separate appointments in separate story worlds.
Key relationships
His most important investigative opponent is Susan Ryeland, whose persistence forces him to revisit material he considers settled. Alan Conway supplies the uncomfortable link between the cases: the novelist has left information in fiction rather than in a clear statement to police.
At Branlow Hall, Derek Endicott is a particularly important witness. Derek’s identification appears stronger when reduced to a simple police conclusion than when Susan asks precisely what he saw. Aiden MacNeil stands before Locke as a missing woman’s husband, a role that brings sympathy and an opportunity to shape the investigation’s public story.
Played by Daniel Mays
Daniel Mays plays DS Locke. Mays also plays DI Chubb. Their resemblance is deliberate dual casting, not a family relationship.
Their story and fate — spoilers
Susan’s Magpie investigation exposes Charles Clover as Alan’s killer. The discovery overturns the suicide explanation and puts her in danger when Charles attempts to destroy the evidence and kill her. Locke’s authority matters once the literary puzzle has led to an identifiable crime.
Moonflower exposes a still more damaging error. Stefan did not murder Parris: Aiden did, and later killed Cecily when she recognised the truth. Derek had seen clothing and equipment associated with Stefan without seeing a face clearly enough to make the identification secure. Susan’s reconstruction separates what the witness observed from what police believed it established. Locke represents the system that must now deal with that correction, not a second secret mastermind behind the crime.
Books and television — book spoilers
Daniel Mays also plays Inspector Chubb inside the Pünd novels. The shared face makes Alan’s borrowing from life immediately visible, but the two officers do not have identical temperaments or identical cases. Chubb can collaborate with Pünd while Locke clashes with Susan.
The adaptation places these relationships beside each other repeatedly. A cut from one investigation to the other lets viewers compare the same actor’s stance, rhythm and response to an outsider. In prose, that correspondence depends on Susan’s recognition and the reader’s memory; television turns it into a visual feature. The useful comparison is how each officer handles another person’s intelligence, rather than whether the same actor means the same solution in both worlds.
Read or listen to the book
Magpie Murders (2016)
Anthony Horowitz’s novel behind the first television mystery.
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Daniel Mays plays both DS Locke and DI Chubb, connecting the two story worlds.