After an extended illness, Ralph Myers’s wife, Jan dies from brain cancer. Blaming the doctors, his family files a lawsuit, which they lose. Ralph decides to show up at a party the doctors have planned and confront them. Unsure of his own intentions, he arrives at a country estate only to find mutilated bodies—hands, arms, and heads—scattered by the pool. In the darkness, Ralph sees a man dressed in dark clothing with blood dripping from the corner of his mouth. As the creature prepares to attack, police units approach and the creature retreats into the woods leaving Ralph to explain what happened.
Terrified by what he has seen, Ralph mourns for his wife. One night, the creature appears in his bedroom and declares that Ralph has ninety days to live. Ralph knows this is his way of torturing him.
Ralph uses a baseball bat to defend himself. The creature is driven away.
Desperate to find the creature and kill him, Ralph visits an old acquaintance, Stephanie Brewster who is a newspaper reporter with access to information Ralph needs. Stephanie loved Ralph before he married Jan and sees Jan’s death as a new opportunity to get Ralph back again. Disbelieving Ralph’s story about a creature he calls Diabolus, she attempts to coerce Ralph back into her arms again. Aware of her scheme Ralph rushes out of her office and out of her life.
Later, while reviewing the case, Stephanie sees an opportunity to capture the creature therefore making herself famous. Studying a picture the police shot that night, she sees Diabolus in the background and thinks she recognizes him. She almost screams when she realizes who he really is.
Horrified, Ralph Myers moves to Crystal Falls, West Virginia. Living an isolated life, he refuses to believe Jan Myers is really dead. Attempting to lead a normal life, he has great difficulties keeping his deadly secrets from a close friend, Maureen Evers who has a crush on him that Ralph is trying to avoid.
Knowing that Diabolus can appear at any time, he reminds Maureen that he is diabetic and too old for her. The harder Ralph attempts to convince her that he is not the one for her the more aggressive she becomes. Maureen owns a local general store where Ralph shops. She is confused because Ralph is a writer of over twenty novels that he has never submitted to publishers. He tells her that the timing isn’t right. She suspects that he on the run and doesn’t want the publicity.
Watching a little league baseball game in a nearby park with Maureen as a severe storm approaches, Ralph sees Diabolus standing by the fence. Warning Maureen that they must escape, they run down an old hikers trail that leads them through thick woods as the storm hits with a ferocity that causes them great suffering. Diabolus pursues them relentlessly.