1987's "Fatal Attraction," 1992's "The Hand That Rocks the Cradle," 1993's "The Temp," and 1995's "Disclosure" all come to mind as "Obsessed" plays out. One of those genre staples wherein a dangerous, unhinged individual becomes severely and, ultimately, violently fixated with another, the film is predictable, trashily entertaining time-filler. As helmed by television director Steve Shill, making his feature debut, and written by David Loughery (2008's "Lakeview Terrace"), there are signs in the first half that it could have been more than that, and this is why disappointment sets in. The villain of the piece—sexy, efficient, and, yes, obsessive office temp Lisa Sheridan (Ali Larter)—is treated in the first half with enough intriguing shades of sympathy that it is a shame the movie tosses away this potentially serious exploration into a sad, unhealthy mind in favor of climactic bursts of violence and a cheapening adherence to convention.

Derek Charles (Idris Elba) seemingly has it all—a beautiful wife, Sharon (Beyoncé Knowles); a precious baby son, Kyle (Nathan Myers, Nicolas Myers); a spacious new home in the Los Angeles suburbs; and a tidy new position as executive vice president to law firm Gage Bendix. When assistant Patrick (Matthew Humphreys) gets sick and must miss a few days of work, ambitious blonde Lisa Sheridan arrives to temporarily fill in. Derek is friendly with Lisa, listening to her boyfriend woes, bonding over music, and sharing a nice conversation and drinks. To him, their relationship is harmless, and he not once even considers the option of cheating on Sharon. To Lisa, however, there is much more between them, and she is going to do whatever it takes for their fantasy romance to become a reality.

"Obsessed" is competently made, not above some egregious displays of clichés—there is, indeed, a heated confrontation in a parking garage, as well as some plate-throwing during an argument—but relatively absorbing for much of the time. Usually stuck in supporting roles, Idris Elba (2008's "Prom Night") deservedly gets the lead role of Derek Charles, and is up to the challenge of portraying this faithful, hardworking businessman who gets so far in over his head that he has no idea how to get out of it. His relationship with Lisa, traveling close enough to the line of what is and isn't appropriate between coworkers that it is easy to see how Lisa might get the wrong impression, is well-developed. In another place, in another time, these two might have actually been ideal for each other. That Lisa is unwilling to accept the reality, getting lost in her own delusions of a life with Derek, is where the conflict arises.

None-too-subtle examples of workplace sexual harassment follow, and the way the film sets up this predicament and then finds ways for Derek to be unable to explain his side of the story before it is almost too late to salvage his family is smart enough to not strain believability. As Lisa, Ali Larter (2007's "Resident Evil: Extinction") is quite arresting, the most fascinating character in the film. Before the script pushes her off the deep end and flirts with making her a stock psychopath, Larter is given the chance to essay a person who feels like a true human being, her disastrously skewed reading of situations and relationships worth feeling sorry for her over.

Unfortunately, director Steve Shill is not brave enough to follow the gradually charged storyline out to a natural, character-oriented conclusion. Instead, he goes for the obvious, with Lisa drugging Derek during a business retreat, and later breezing into Derek's and Sharon's home while they are out to dinner, spending time with their baby and ransacking their bedroom. The third-act brawl between Sharon and Lisa is expected—curiously, Sharon is the instigator of the knock-down fight—and worth some fleeting excitement. As it turns out, this is also the film's biggest flaw, dislocating the root predicament between Derek and Lisa simply so there can be an action-oriented, to-the-death finale where Sharon spouts one-liners and calls Lisa a bitch while dragging her across the floor and smashing her face into the upstairs banister.

Certain audiences will be cheering by the end of "Obsessed," particularly fans of Beyoncé Knowles (2008's "Cadillac Records") who are there to see nothing more than the former Destiny's Child singer kick some white-girl booty. Knowles is perfectly respectable in the part of Sharon, but the wannabe crowd-pleasing conclusion that utilizes her to her fullest is guilty of being pure run-of-the-mill silliness that demeans the character of Lisa and deems her to be unworthy of receiving the professional psychological help she needs. By ending on a freeze-frame that brings no insight into anything and solves the plot in the most rudimentary fashion imaginable, "Obsessed" runs out of last straws. There is no excuse for a dumb thriller when the people behind it prove capable enough to make an intelligent one.