``This is just a condominium that offers a few more services,'' Karen Merrick tells Sgt. Ray Koepp and his partner Margaret Loftus, summoned to Friars' Close when Dr. Issac Steiner, one of the Planners of this academic experiment in group living, is stabbed to death. So much for Friars' Close self- approving commitment to nonviolence, thinks Koepp smugly, little realizing that before he's run through the capacious list of suspects (fellow Planners Paul Merrick and Leon Jaroff, Paul's colleague and lover Elizabeth Maklin, skulking maintenance man Charlie Tirquit et al.), he will have killed one of them himself. The late Dr. Steiner wastes no time revealing himself as a thorough scoundrel whose extra services were so seamy--drug dealing, psychological bullying, sexual blackmailing--that every one of his cooperative living partners might well have been delighted to pull the plug on him. But the central mystery here swirls around seductive, enigmatic Karen Merrick, whom former priest Koepp (Profily, 1994, not reviewed) finds himself bewitched, bothered, and bewildered by--even as he acknowledges that she's far and away his most likely suspect. Painstakingly laid out, with a solution that may well catch you off guard; it's the middle range, with its interminable peeling away of guilty secrets, that lags.