Sir Oswald (the steel magnate) and his wife are renting the country home Chimneys. They are hosting a group of young people for several days—Jimmy Theisiger, Gerald Wade, Bill Coleman, Ronnie Devereux, Socks Daventry, Nancy, and __________. The group decides to play a joke on "amiable young ass" Gerry Wade—rousing him up extra early with the help of eight alarm clocks! But the next morning, when the entire house has been wakened by the loud ringings of the clocks, Gerry does not appear. Finally, the butler discovers Gerry has died during the night, of an apparent overdose of sleeping potion. Strangely, seven of the eight alarm clocks have been arranged on the mantelpiece.

A few days later, the rental period is over, and the owners move back in—Lord Caterham and his daughter, Lady Eileen (Bundle). As Bundle is writing letters, she discovers a letter Gerry Wade had been writing to his step-sister on the night he died; the letter mentions "Seven Dials" and asserts that it’s no joke. Bundle mails the letter to the step-sister, and might have let the matter rest there, but the very next day a dying man stumbles out in front of Bundle’s car. Before he loses consciousness, he says, "Seven Dials ... tell ... Jimmy Theisiger." Later Bundle learns the dead man was Gerry Wade’s good friend, Ronnie Devereux. Bundle now suspects that Gerry Wade’s death was not suicide.

The second mention of Seven Dials makes Bundle determined to uncover what the Seven Dials is and find out who killed Gerry Wade and Ronnie Devereux. Before long, Bundle discovers that the Seven Dials is a secret society of seven members, who meet in a sound-proofed room and wear masks! She joins forces with Jimmy Theisiger, Bill Coleman, and Gerry’s step-sister Lorraine to investigate the mystery of who these seven masked members are, and why they killed Gerry and Ronnie.

Spoilers ahead! Scroll down for full spoilers of this book.

At the end of the book, Bundle learns that the Seven Dials club is actually a group of young crime fighters that includes her friend Bill! The mysterious No. 7 who’s never seen at the meetings is actually Superintendent Battle!

If Seven Dials is the good guys, who killed Gerry Wade and Ronnie Devereux? None other than the good friend of Gerry, Ronnie, and Bill’s: Jimmy Theisiger—with the help of Gerry’s step-sister Lorraine. Jimmy and Lorraine are in love and have been a secret couple for years.

Gerry, Ronnie, and Bill were all founding members of the Seven Dials club. They were investigating certain security leaks from the Foreign Affairs office where they all worked. Gerry was closing in on Jimmy being the culprit, but before Gerry could act, Jimmy put a lethal dose of sleeping potion in his whiskey. Then Ronnie began to suspect, so Jimmy and Lorraine shot him. At the end, they try to do away with Bill and Bundle, too, but their plan fails.

Finally, Bill and Bundle get engaged, and Bundle agrees to become a member of the Seven Dials club.

The Seven Dials Mystery is one of my favorite Agatha Christie books. I like the atmosphere of the Roaring 20s. Also, Bundle is a really well-written heroine in the style of Tuppence (The Secret Adversary), Frankie (The Boomerang Clue), or Anne Beddingfeld (The Man in the Brown Suit). She’s spunky, brave, determined, and curious.

The gang motif is fairly common in Christie’s early books. In this book it’s especially effective, because of the theatrical mystery of the members—also the undercurrents of espionage, the beautiful foreign woman, a valuable "formula" that must not fall into the wrong hands, etc. You feel like you’re really experiencing an adventure.

Overall, this is a really good book but not an amazing mystery. I think there *are* clues for the reader to guess the mystery, but not too many. (More of the interest of the book is the personalities and the world they live in.) However, once you know who the villains are, you can re-read the book and see all the little hints throughout.