|If it weren't so damn good, we'd be chiding it for its similarity to Play Misty for Me (1971) and Daddy's Gone A-Hunting (1969).
As it is, this gem of a thriller has all the right moves to stand on its own & create its own power and scares.
Married guy Douglas has a brief sexual fling with Close. Not a good move. For Close is a psycho-in-waiting who, once scorned, turns the tryst into a permanent vendetta of revenge.
Exceptional performances all around (Archer is superb as the understated, tormented wife dealing with her husband's fidelity), good pacing, and superbly ratcheted drama all add up to place this at the top of the "soap opera with knives" subgenre.
The Friday the 13th climax supplanted an alternate, more subdued ending in which Douglas is suspected of murdering Close.