Marble Hall Murders

Marble Hall Murders by Anthony Horowitz was originally published in 2025. It is the third novel in the Susan Ryeland series. The previous installments, Magpie Murders and Moonflower Murders, were adapted by Horowitz for PBS Masterpiece. Marble Hall Murders is a mystery novel about a literary editor and includes a book-within-a-book, or an embedded narrative, Pund’s Last Case. The novel follows editor-turned-detective Susan Ryeland as she investigates a new murder linked to her late author’s final manuscript. Horowitz explores The Weaponization of Blurring Fiction and Reality, The Toxic Weight of Family Secrets, and Power, Control, and the Editorial Gaze. Horowitz has written many other series, including a continuation of the Sherlock Holmes series.

This guide cites the HarperCollins hardcover edition.

Content Warning: The source material and guide feature depictions of physical abuse, animal cruelty, child abuse, substance use, death by suicide, graphic violence, death, illness, sexual content, and racism.

Plot Summary

Literary editor Susan Ryeland is freelancing for Causton Books. Her boss, Michael, gives her a new assignment: a continuation of the Atticus Pund series. Susan worked with the original author, Alan, on the series when she worked at Cloverleaf. Her former Cloverleaf boss, Charles, killed Alan and tried to kill Susan. The new author is Eliot Crace, grandson of famous children’s author Miriam Crace.

Two sections of Pund’s Last Case by Eliot are included as an embedded narrative set in the 1950s. Atticus is retiring as a detective because he has a terminal brain tumor. He runs into an old associate, Margaret Chalfont, at the doctor. She is leaving London for the South of France and asks if she can write to him. Her letter is a plea for his help. She heard her husband, Elmer, say something disturbing and wants Atticus to investigate. Because she is an old friend who is also dying, Atticus agrees to go to the Chateau Belmar.

Margaret is already dead when Atticus arrives with his assistant, James. Police officer Frederick Voltaire joins them. Margaret’s children have financial issues, and she is giving them small stipends. Elmer will inherit most of her fortune. There are many clues that point to Elmer being the murderer. For instance, someone with white hair like his purchased poison the day that Margaret died. Margaret’s lawyer, Lambert, was coming over to talk about Margaret’s will the day that she died. Eliot’s incomplete manuscript ends on a cliffhanger: Atticus says that shoe polish is the key to the whole mystery. The embedded mystery begins as a self-contained narrative, but its relevance becomes clear as Susan investigates Miriam’s murder and learns about the Chalfont family’s secrets, suggesting Eliot used real people as inspiration.

Eliot reconnects Susan with Elaine, Charles’s wife. Susan got Charles imprisoned for killing Alan, so she’s hesitant to rekindle their friendship. Elaine tells Susan that Miriam was vile, but the family had to keep quiet about it to access her money. Charles worked with Miriam on a few of her books before she died.

Susan researches Eliot’s family, as there are many connections between his novel and real life. She talks to Frederick, Miriam’s adopted son, who runs the Marble Hall Museum—part of Miriam’s estate. Frederick praises Miriam. Jonathan, Eliot’s uncle, doesn’t want Susan causing a scandal, as Miriam’s estate is making television and film adaptation deals for her children’s books.

Eliot’s brother, Roland, works for Jonathan and is willing to privately say negative things about Miriam that echo what Elaine and Eliot say: Miriam was cruel and manipulative. Susan learns that Roland is sleeping with Eliot’s wife, Gillian. Eliot hits Gillian when he discovers she is pregnant with Roland’s baby.

At the party for the anniversary of Miriam’s death, Eliot drunkenly declares he knows who killed Miriam and will reveal it in his book. He publicly insults and fires Susan. As he leaves the party, he is killed in a hit-and-run accident. Elaine frames Susan for Eliot’s murder, calling in tips about her car and planting evidence. The detective in charge of Eliot’s case, Ian Blakeney, doesn’t think Susan is the killer.

Susan visits Charles in prison to ask him about Miriam and Eliot. Charles pitied Eliot because Miriam was cruel to him and gave Eliot a book deal. Eliot’s novels didn’t sell well. Eliot confided in Charles that he saw Roland with poison the night before Miriam died. However, Charles will later deny this; he is toying with Susan and wants her to get arrested for Eliot’s murder. Elaine destroys Susan’s apartment and wounds her cat while Susan is with Charles.

Susan asks for Blakeney’s help after the break-in. He shares Eliot’s notes about the ending of Pund’s Last Case and reads the chapters Eliot finished. Blakeney and Susan uncover who Eliot’s murderer is in the novel, and Blakeney decides to write the final chapter.

In Pund’s Last Case, Robert, Roland’s literary counterpart and Margaret’s stepson, masterminds Margaret’s murder. He makes sure Margaret overhears Elmer talking with an art historian about how his gallery is trading in art that was stolen from Jewish families during World War II. Then, he gets Lola, the wife of Jonathan’s literary counterpart, Jeffrey, to call Lambert pretending to be Margaret asking to talk about the will. Robert impersonates his father by using white shoe polish to color his hair and buys the poison. He also seduces Lambert’s assistant, convinces her to help deceive the pharmacist, and kills her. Robert Waysmith’s name is an anagram for “it was my brother.”

In real life, Eliot believed Roland killed Miriam. However, Susan discovers that Frederick was Miriam’s biological son from an affair with her chauffeur, Bruno. After Frederick was born, Miriam fired Bruno, and he died in poverty before Frederick could meet him. Frederick killed Miriam after he discovered the truth about his father. He then killed Eliot because he thought Eliot’s novel would frame him as Miriam’s killer.

When Susan confronts Elaine about framing her for Eliot’s death, Elaine tries to kill Susan. Blakeney saves Susan and arrests Elaine. Susan starts her own publishing company, Nine Lives Books, and buys the rights to Pund’s Last Case from Michael. Blakeney, writing under a pseudonym, completes the novel, and they publish it. Susan publishes a tell-all biography about Miriam, which destroys the deals for her intellectual property and hurts sales of her books. Susan and Blakeney fall in love, and Susan vows to never work on an Atticus Pund novel again.