Rosario Dawson is the prey of her fiancée’s ex in “Unforgettable.”

Julia Banks (Dawson) bids adieu to her best friend (Whitney Cummings) and job at a popular publishing company in San Francisco to live with her fiancée, David (Geoff Stults), in a smaller Californian town near the mountains.

This new living arrangement provides obstacles for Julia including getting to know Lily (Isabella Kai Rice), David’s young daughter, and Tessa (Katherine Heigl), David’s ex-wife who spends too much time with them.

During a shindig to celebrate David’s brewing business, Tessa glances at text messages on Julia’s phone. She learns that Julia and David are engaged. Houston, we have a problem! Tessa snatches Julia’s phone when she’s not looking and uncovers dark secrets, including an old relationship with one Michael Vargas (Simon Kassianides), whom Julia filed a restraining order against several years ago.

Julia questions Tessa’s motives after learning from David’s friend that Julia became possessive and treated David as her precious like Gollum and his ring from Lord of the Rings. He ended things with her and she didn’t take it too well.

“Unforgettable” is a thriller that pushes the envelope in the obsessive lovers department. Sure, the plot stems from Clint Eastwood’s Play Misty for Me, Martin Lawrence’s A Thin Line Between Love and Hate and Beyoncé’s Obsessed, but there’s a twist. Tessa reaches the height of her insanity and Julia shows her reflection in the mirror. Tessa sees how crazy she’s become. In the previous thrillers, the psychopaths don’t know how crazy they get. They stay crazy until they die. But Tessa briefly gains her humanity thinking, Am I a monster?

Heigl is superb as a crazed ex-wife. Tessa is a real-life Barbie doll. She’s perfect and obsesses over having a perfect life. When David ends it with her, she can’t move on. She’ll do anything to get him and her old life back. Dawson is incredible as Julia who only wants to fit in with her new surroundings and live a happy life that neither of her parents had.