In March of 1926, Daisy Dalrymple Fletcher and her friend and collaborator Lucy (a.k.a. Lady Gerald) head off for several days at stately home reputed to have the best grotto in the country. Working on a book of follies (architectural), they plan to research and photograph it. Leaving her husband and young twins behind, Daisy is expecting a productive weekend at Appsworth Hall, with the only potential difficulty being keeping Lucy from offending the current owner, a manufacturer of plumbing products. Alas, it's not to be quite so simple. At the home, they find themselves faced with a curious assortment of people including the abominable, tactless Lord Rydal, who is rumored to be having an affair with one of the guests while at the same time in ardent and artless pursuit of the hand in marriage of another. When the grotto explodes with Lord Rydal in it, it's not a question of who would do it—as most who've met him would be sorely tempted—but who actually did do it.
At the start of Dunn's sprightly 18th Daisy Dalrymple mystery (after 2008's Black Ship), Daisy travels to Wiltshire because she's writing a book about an architectural folly, an elaborate grotto, at Appsworth Hall, owned by Mr. Pritchard of Pritchard's Plumbing Products. Best friend and freelance photographer Lucy Binscomb (aka Lady Gerald) accompanies Daisy, who leaves behind her husband, Scotland Yard's Det. Chief Insp. Alex Fletcher, to look after their twin children. On arrival at Appsworth, Daisy and Lucy discover that Mr. Pritchard is hosting a lavish house party, which includes eligible bachelorette Julia Beaufort; Lord Rydal (aka Rhino); Lady Ottaline Wandersley (with whom Rhino is having an affair); and Charles Armitage, a Canadian charmed by Julia. A shocking grotto explosion that takes Rhino's life spares Lady Ottaline and Rhino's chauffeur. While Dunn's cozy confection doesn't offer a lot of surprises, it does a neat job of evoking upper-class life in 1920s England.