'Marble Hall Murders' Greenlit to Complete Susan Ryland Trilogy

We are in a golden age of murder mysteries on TV. Cozy crime like Grantchester, Father Brown, and Death in Paradise are all hitting double-digit seasons. Meanwhile, more highbrow fare aims to do something different with the genre, from Agatha Christie reimaginings like Murder Is Easy to upcoming comedy mysteries like Ludwig and Death Valley. But there's nothing on TV quite like Anthony Horowitz's Susan Ryeland stories, adapted from his own novels Magpie Murders and Moonflower Murders, which take a meta-view of the genre by enclosing a period piece mystery inside a contemporary one. Now, the third and final story, Marble Hall Murders, has been greenlit to complete the trilogy.

In an interview with Horowitz last fall during Moonflower Murders' run in the fall of 2024, the author confirmed Marble Hall would be the third and last installment of the novels, partly because he never meant for it to be two books, let alone three. "Magpie Murders was an extremely difficult book to write," he told Telly Visions in October 2024. The logistics of writing a period-piece mystery within a present-day mystery took several years, so despite his wife and executive producer Jill Green's suggestion that making it a series would be easier to sell as a TV adaptation, his first reaction was: "It was a bit of a horrific thought."

Horowitz eventually dreamed up Moonflower Murders, but he had no plans for a third book until filming for the second series commenced, and he realized how much he enjoyed working in this meta-fiction world he'd created. However, though Marble Hall will bring back Lesley Manville as Susan Ryeland and Tim McMullin as Atticus Pund, those are the only cast members Horowitz's novel plans to keep, making it less-than-ideal for TV audiences, but very much in keeping with Horowitz's idea of digging into the process of writing and reading mysteries.

Here's the official synopsis from Masterpiece:

Susan Ryeland returns, a book editor with an uncanny knack for embroiling herself in murder mysteries. The latest case sees her back in England, where she becomes entangled in a new Atticus Pünd mystery penned by an emerging writer. Set in 1955 at a luxurious Corfu villa, “Pünd’s Last Case” harbors more than just fictional intrigue – a real killer’s identity lies hidden within its pages, putting Susan in mortal danger once again. Pünd, the literary detective who transcends the page, returns to aid Susan in solving the murder of Miriam Crace, described as the world’s most celebrated children’s author.

Manville (Sherwood) and McMullen (The Crown) are the only cast members confirmed to return, consistent with what Horowitz told us about his final book in the series. "It's different; Alan Conway doesn't appear, nor do quite a few other characters whom we know and love," he explained. Now that Conway has been dead for a few years, "a new writer has been shipped in," Elliot Krace, as "a continuity author." 

According to Horowitz, "Krace is a very damaged character with a dark secret buried in his childhood. He's hiding that secret in his book even as he writes it, and Susan realizes he could be writing a suicide note. So, she's trying to help and stop him from getting into trouble. I can’t wait to cast him; Elliot is the most wonderful part to play. He is a sort of devil and, at the same time, so sweet, damaged, and sad. He's a lot of things, and his relationship with Susan Ryeland…I think Lesley will have a lot of fun with it."

Horowitz will once again pen all six episodes adapted from his novel. Director Rebecca Gatward will return to helm all installments, and Suzanne McAuley will produce. It is executive produced by Green for Eleventh Hour Films and Susanne Simpson for Masterpiece.

Marble Hall Murders (the novel) will hit bookshelves and Kindles on Friday, March 13, 2025. Filming will also commence in March, with plans to shoot in Dublin, Corfu, and London. No release date has been set, but it's a good bet the series will debut in 2026. Until then, all episodes of Magpie Murders and Moonflower Murders are streaming for members on PBS Passport.