In the psychological thriller 'Obsessed', Beyoncé Knowles stars as Sharon Charles, a smart young woman with a charmed life. She has a handsome husband, Derek (Idris Elba); a sweet young son; and they’ve just moved into their dream home thanks to Derek’s recent promotion.

Then one day Derek meets a new temp at the office: Lisa (Ali Larter). Beautiful, poised, and perpetually cheerful, Lisa is the perfect co-worker. Soon Derek finds her crying at work over a boyfriend and tries to comfort her. Then Lisa comes on to him at the company Christmas party, and he firmly tells her she’s got the wrong idea.

The next day she tries again. Lisa won’t take no for an answer, and begins to come more and more unhinged with each and every refusal. Soon, Derek becomes terrified by how far it appears Lisa’s obsession will go.

At first Derek says nothing about Lisa to his wife, thinking he has things under control. He resolves to fire her but finds she’s already quit, and he believes Lisa is gone from his life. But a few weeks later, Derek receives a series of eerie, sexual e-mails, all from the same sender: “TEMPGIRL.” Then Lisa shows up at his office retreat. Sharon is pulled into the triangle as Lisa builds a case against Derek in an effort to drive a wedge between he and his wife.