Though slavishly modeled on Rosemary's Baby--the uptown Manhattan locale, the attractive young couple, the friendly (evil) elderly neighbors--this horror teaser is more silly than scary. But the breezy mindlessness here is easy to take, especially since it can all be read as a macabre (perhaps unintentional) send-up of the jogging/health-food craze. Jackie Lawrence (of Henri Bendel) and husband Pete (big in publishing) have been desperately hunting for a new apartment in impossible Manhattan--and then, eureka! While jogging in Central Park, Pete meets a group of glowing middle-aged jogging couples (""every one of them Jack LaLanne lookalikes"") who invite him to rent a dream apartment in the building they share in N.Y.'s poshest neighborhood. Wonderful--and soon Pete eagerly falls in with his neighbors' obsessive physical fitness (exercise, health foods, etc.). Even reluctant Jackie, spurred on by jealousy of one of Pete's svelte jogging companions, gets in the all-natural swing. But Jackie begins to feel uneasy when she realizes that the other young people in the building are--like the Lawrences--orphans; and then those other young couples move out, disappear without a word! And what's going on in the locked basement laboratory? Could it have something to do with the fact that those middle-aged-looking couples are really in their late 80s--or with Jackie's miscarriage, or the ""suicide"" of one of those disappearing neighbors? Poor Jackie: just like Mia Farrow, everyone thinks she's being paranoid. And then it's too late, as the old folks explain to doomed Pete and Jackie--at great foolish length--just what we've suspected for 200 pages: ye olde rejuvenation-viahuman-sacrifice bit. Nonsense, through and through, without a glimmer of the glow of Ira Levin's narrative knack; but, except for those final explanatory pages and some sub-literate prose (""The sky would have turned on El Greco""), it's harmless and swift, with a few chuckles to compensate for the shortage of chills.