Boxing Day 1935. A snowed-in manor on the very edge of Dartmoor. A Christmas house party. And overhead, in the attic, the dead body of Raymond Gentry, gossip columnist and blackmailer, shot through the heart. But the attic door is locked from the inside, its sole window is traversed by thick iron bars and naturally, there is no sign of a murderer or a murder weapon. Fortunately (though not for the murderer), one of the guests is the formidable Evadne Mount, the bestselling author of countless classic whodunnits. In fact, were she not its presiding sleuth, The Act of Roger Murgatroyd is exactly the type of whodunnit she herself might have written.