Jeannie and William Costigan have the ideal life: A solid marriage, a beautiful daughter, Trish, and an enviable house in an upscale neighborhood. But as in all relationships, there are some problems. William, the General Manager of a local TV station, spends far too much time at the office. Jeannie, a successful columnist, has suddenly found herself unemployed. As a result, their love life has lost its fire. Yet they've weathered bigger storms and survived- like the affair William had five years ago ...

They are not, however, prepared for Donna Germaine, a woman with a pretty-face and a secret past, who moves into the house across the street with her Aunt Grace.

Not long after Donna's arrival, the Costigan's world begins to unravel. It all starts innocently enough at a barbecue hosted by Jeannie and William. Donna meets Jeannie, Jeannie's friends, Jeannie's daughter, and Jeannie's husband . . . William.

For William, Donna is attractive and seems nice, but nothing more. For Donna, William everything. He's the man she's been searching for her entire life. She decides she must have him and that she will have him.

Donna quickly gains the Costigan's trust, first becoming Jeannie's friend and Trish's babysitter, and eventually, after her aunt's tragic death, a helpful employee at William's TV station.

She's the perfect neighbor ...

But Donna finds her path to William blocked. First by her aunt, who discovers her intention to have William at all costs, and then by Ashley, William's gorgeous assistant who, in Donna's mind, is competition.

Donna kills Aunt Grace first, making it look like an accident. She then murders Ashley viciously, but not before planting evidence of an affair between Ashley and William in Ashley's apartment.

Naturally the police question William about this alleged affair. He denies it, but realizes they will talk to Jeannie too, and she will learn of an innocent business trip he took with Ashley that he kept a secret in order not to give Jeannie a reason to worry.

Jeannie doesn't buy William's claim of innocence and in a fit of rage takes Trish and leaves ...

Finally William is alone and vulnerable, just the way Donna had planned. In her delusional mind the rest of the story is written: William will discover his intense feelings for her, and they will live happily ever after ...

After Jeannie gathers her thoughts and battered emotions, she decides to fight for her marriage and heads home unaware of the danger that now awaits her in her very own house.