This wild romp into respectable Cape Cod is proof that the author of Guns in the Heather (1963) has mastered the art of writing a juvenile mystery. Once again the hero is Posy Flower, who is somewhat of a teen-age James Bond. Posy proposes to spend the summer holidays tutoring twins, and is led up to their Cape Cod home in a hearse to the accompaniment of pistol shots -- a suitable introduction to this unusual establishment maintained by an embalmer named Sarx, who is wild over mummies. Suspense develops with the discovery that Sarx intends to prepare the members of his household for ""eternal life"" and grows with the chase after him and his Arab assistants. This intricate and far-fetched adventure, with its extraordinary collection of characters, maintains a fast clip, hovers within the bounds of credibility, and includes frequent touches of humor as well as attention to the numerous details which distinguish a genuine mystery.