Another puzzle for Calleshire district's Inspector C.D. Sloan and thickheaded sidekick Detective Constable Crosby (Last Respects, etc.). Lucy Dumast stands accused of the poison murder of Kenneth Carline, an employee in her father's engineering firm. She refuses defense counsel, is mute in court and is jailed for contempt. Her father is in deepest Africa overseeing construction of a new town, while the windup of his local tunnel project is conducted by Ronald Bolsover, deputy chairman of the company. Sloan gets the case with a brief to review all the evidence. Meanwhile, matters are complicated by the seemingly senseless murder of Hortense Fablon, French au pair girl of Lucy's friend and neighbor Cecelia Allsworthy. The intuitive Sloan puts together a lot of little inconsistencies to come up with a big motive and a surprise killer. The author's unrestrained use of pedantic, mostly dreary asides has never been more in evidence--or more damaging--to a trimly developed plot. The end result is, unfortunately, irritation rather than satisfaction.