A series of baffling murders among a group of imprisoned agents threatens the outcome of World War II in this chilling mystery from the New York Times best-selling author of Mr. Churchill’s Secretary.

November, 1942. World War II is raging, and former spy Maggie Hope knows too much: what the British government is willing to do to keep its secrets, who is lying, who the double-crossers are. She knows exactly who is sending agents to their deaths. These are the reasons Maggie is isolated on a remote Scottish island, in a prison known as Killoch Castle.

When one of her fellow inmates drops dead in the middle of his after-dinner drink - he’s only the first. As victims fall one by one, Maggie will have to call upon all her wits and skills to escape - not just certain death...but certain murder.

For what’s the most important thing Maggie Hope knows?

She must survive.

Praise for The Prisoner in the Castle:

“The colonel sums it up best on page 10: ‘If you take a pretty girl and teach her how to kill, it can cause problems.’ Not just problems - electrifying action and nonstop surprises. I loved this book!” (R. L. Stine, author of the Goosebumps and Fear Street series)

"One pleasure of a mystery series is connecting with a character that changes and grows with each novel.... Maggie's intelligence and loyalty to the war effort continue to evolve in [Susan Elia] MacNeal's series.... Solid twists keep the plot of The Prisoner in the Castle churning until the surprise finale." (Associated Press)

"Evocative." (Publishers Weekly)