The wolf-in-sheep's-clothing thriller was a hoary cliché even before its early-'90s renaissance in the form of Poison Ivy, Single White Female, and The Hand That Rocks the Cradle. This workmanlike straight-to-video effort tweaks the familiar formula as the hidden killer turns out to be not a vivacious woman but a strapping young lad instead. Such slight variations aside, Natural Enemy goes pretty much by the books, from the villain's sinister yet convincing assimilation into the lives of his victims to the extended scenes of revelation and violent retribution at the end. Despite some nasty subtext about gender and sexual orientation, though, director Douglas Jackson gets decent mileage out of his modest budget, milking his inventive set pieces for all they're worth and eliciting generally strong performances from his small cast. Old pros Donald Sutherland and Lesley Ann Warren, in particular, do their best to give the stock scenario emotional resonance; he plays the sort of role Michael Douglas might have bagged if this weren't a B-movie, while she provides carefully preserved sexiness and emotional vulnerability as a woman whose difficult choices come back to haunt her later in life. Despite his experience in a similar role in Copycat a few years earlier, however, William McNamara brings nothing new to his preppy, pretty-boy psycho; he overplays wildly, abetted by the implausibilities in Kevin Bernhardt's script. Tia Carrere, meanwhile, gets only a few scenes of crisp sex appeal before she's revealed as a mere plot device. Still, there's something satisfying about an unpretentious genre effort that pushes the correct creepy buttons fairly effectively. Natural Enemy is sure to entertain the many insomniacs who encounter it accidentally on late-night cable.