As some readers might guess from the title, this fourth outing for narrator-sleuth Mallory is steeped in rueful nostalgia for the youth-generation of the 1960's--but Collins' variation on The Big Chill is shrewd, ironic, and specific enough to rise several notches above the usual sentimentality and romanticization. Mallory--a mid-30s mystery writer based in Port City, Iowa--is deeply upset when he hears that his old high-school pal Ginnie Mullens has committed suicide in nearby Iowa City. But was it suicide? Snooping around, Mallory soon finds that willful, adventurous Ginnie--an erstwhile hippie/ druggie/radical with a deep, ambitious entrepreneurial streak as well-had lots of enemies: bitter ex-lovers; a nasty sibling rival; seamy drug-dealing colleagues; an old flame with a new cause for rage (revelation of a bygone abortion). So the sleuthing leads to a variety of aging Sixties types, to old high-school chums, and to Las Vegas (where Ginnie often, intensely gambled)--while Mallory also finds time to begin an engaging, seemingly serious romance. The mystery here-which turns on Ginnie's odd blend of money-hunger, rebelliousness, and quirky idealism--is less than completely satisfying or convincing. But along the way Mallory manages to be both comic and touching as he takes a nicely balanced view of the hippie-to-yuppie transformations of the past two decades. (""Look around this downtown,"" says a Vietnam vet about Iowa City. ""It looks like Disneyland if Joan Baez invented it."") Wry, flavorsome, quick and crisp--and the best work so far by busy mystery-man Collins (who also writes the Dick Tracy comic strip and heavy-handed period crime-tales like True Detective).