It's Christmastime in Cambridge's Harvard Square, but goodwill is in short supply. Busy, warmhearted stage director Sarah Bailey is once again running the annual Christmas Revels--a complex, multifaceted production involving morris dancing, drama, song, and scores of volunteers. Sarah is married to insanely, secretly jealous Morgan, a respected ornithologist who's embarked on a program of eliminating, one by one, the men he thinks might steal his wife--the first of whom is folksinger Henry Shady, struck by Morgan's car in a seemingly unavoidable fatal accident. Mary Kelly, wife of ex-detective, now Harvard teacher Homer (Divine Inspiration, 1993, etc.), observes the incident and is troubled by doubts about it. Meanwhile, a ragged group of homeless, under the direction of self-aggrandizing activist Palmer Nifto, has set up a tent town on an overpass beside Harvard Yard. Palmer works to extract money, property, and promises from Harvard officials, making sure the media is ever-present. As Morgan's hit list expands and two more cohorts die, Sarah's burgeoning suspicions are reinforced, along with those of Homer Kelly--just in time to save the last prospective victim. Little detection, little suspense--but a plentitude of mini- lectures on ornithology, astronomy, and Harvard's architecture and history. This time out, the incisive terseness of the author's straightforward illustrations is nowhere present. A loquacious narrative that's only fitfully absorbing.