I.O.U.

The layered plot of the latest in the excellent Jenny Cain series ( Say No to Murder ) finds the Port Frederick, Mass., sleuth probing the cause of her recently deceased mother's insanity. Cain discovers that her mother's mental collapse many years before coincided with the bankruptcy of the family business. The closing of Cain Clams created considerable unemployment locally and countless enemies for the Cains--one such foe may now be trying to prevent the amateur detective from delving further into her family's past and the town's secrets. As she tracks down public mysteries, Cain unearths painful personal issues; an attempt on her life, construed as an effort at suicide, forces her to deal with the legacy of her mother's madness. Pickard masterfully resolves both plot lines in this affecting, provocative novel centering around the mystery at the heart of mother-daughter relationships. (Apr.)