The story centers on two women. Catharine (Theresa Russell) is a psychopathic ''femme fatale'' who preys on wealthy middle-aged men, seducing them into marriage and then fatally poisoning them. Each death is misdiagnosed as ''Ondine's curse'', a condition by which seemingly healthy middle-aged men die in their sleep. United States Department of Justice agent Alexandra "Alex" Barnes (Debra Winger) stumbles onto the first murder while investigating another case. As Alex delves further into the case, she uncovers a pattern which she believes ties the same woman to several similar murders.