Shock!, a novel by Virgil Markham, was first published by Collins Crime Club in 1930. The title is exuberantly melodramatic; in the US, the book was called The Black Door. But the splendid sub-title is as prolix as the title is concise, and reads: "The Mystery of the Fate of Sir Anthony Veryan's Heirs in Kestrel's Eyrie Castle near the Coast of Wales". A sub-sub title adds: "Now set down from information supplied by the principal surviving actors, and witnesses". Wow!
One delightful feature of my copy is that it contains a massive pull-out folded family tree of the descendants of Horace Veryan. Some addenda to the tree, although printed, appear to be handwritten, bringing the toll of fatalities in the family up to date. And there is more! A map of the local area, featuring St David's and Ramsey Island, is included. And there are plans of the ground and first floors of Kestrel's Eyrie.
The viewpoint character is Tom Stapleton, an American (as was Markham) who is a member of the seemingly cursed Veryan family, and who is in Wales, hoping to see Sir Anthony Veryan, recently incapacitated following a murderous attack. He finds himself embroiled in a complicated mystery in the finest Golden Age tradition. Markham has a nice plot twist up his sleeve, although I anticipated what he was planning to reveal, despite finding myself bogged down by the minutiae of the story.
This is an enjoyable vintage mystery, not as good as Markham's first book (also set in Wales), Death in the Dusk, but quite entertaining as long as one reads it quickly, and doesn't pause to quibble about details. My copy once belonged to Dorothy L. Sayers, who obligingly signed it. It came from the late Bob Adey's collection, and although it's by no means a masterpiece, it has fired my interest in Ramsey Island. I've visited St David's, long ago, but not Ramsey. It's an omission I really must repair.