Not for nothing is "A Stranger Is Watching" set, literally, at sewer level. If other horror films have hit rock bottom, this oppressively grisly and grimy creeper is positively subterranean. It is now playing at several unlucky area theaters.

Director Sean S. Cunningham has gone from the playful gore of "Friday the 13th" to the mere stupid ugliness of "Stranger," a film that opens with a woman being raped and bashed to death in front of her 8-year-old daughter and actually manages to descend even from there. A few years pass, the wrong man has been imprisoned, and the stranger returns to kidnap the girl and the father's new lady friend and drag them off to a filthy hovel under the Oyster Bar at Grand Central Station.

Since the stranger (Rip Torn, certainly seedy- and sleazy-looking enough for the role) is depicted as a psycho, no motive need be given for his brazen gambit or peculiar modus operandi. While in his clutches, the child and the woman (Kate Mulgrew) repeatedly try to escape, only to be dragged back and slapped around. Finally the villain sticks a chisel into the woman's side, and she crawls, bleeding, into the filthy underground tunnels in an effort to escape.

It's the most unpleasant and unsavory kind of suspense movies can generate, and it is relieved only by moments of additional incidental violence; the villain gets beaten by thugs in a men's room, and later throws a butcher knife into the chest of his drunken accomplice. The screenplay is by Earl Mac Rauch and Victor Miller, and if they were up to anything other than viciousness, they kept it a deep, dark secret.