Sixtyish Dorothy Martin, a widowed American now living in the English village of Sheresbury (Trouble in the Town Hall, 1996, etc.), happily accepts an invitation from friends Tom and Lynn Anderson to spend two weeks on the tiny island of Iona in Scotland. When Tom's illness delays the couple's departure, though, Dorothy makes the journey alone. Discovering that she's left the key to their cottage at home, Dorothy checks into a small hotel run by Hester and Andrew Campbell. A group from Illinois is also staying there--the winners of a contest to find the most community- dedicated members of various Chicago churches, with Rabbi Jake Goldstein subbing for a Quaker winner stricken with appendicitis. Iona is a stop on their tour, and no one seems happy about it--or with one another: Sister Teresa, a feminist nun in mufti; elegant Unitarian Grace Desmond; Hattie Mae Brown, a Baptist choir leader; Lutheran organist Chris Olafson; unctuous, unpopular youth leader Bob Williams; and short-fused garden-designer Janet Douglas, a Presbyterian. A sight-seeing excursion to Fingal's Cave makes a slow-moving Dorothy, arriving after others have left, the only witness when Bob Williams falls to his death from a rocky height. She becomes obsessed with the idea that the fall was murder, not accident, and spends the rest of her stay trying to prove it. Some interesting characters, a graphic description of a humongous storm, and a picture of the island's craggy isolation are well done. But Dorothy's relentless and self-absorbed maunderings, along with a nearly nonexistent plot, bring the third in this series closer to chatty travel guide than mystery.