Katherine Heigl and Rosario Dawson Exchange Heated Words in 'Unforgettable' First Look

Photo: Karen Ballard/Warner Bros

Katherine Heigl is going toe-to-toe with Rosario Dawson — in their new movie, that is.

Heigl stars as a scorned ex-wife whose jealousy for her ex-husband’s new fianceé Julia (Dawson) quickly takes a pathological turn in the upcoming thriller Unforgettable.

“It was deliciously exciting going toe-to-toe with Katherine, whose well-crafted nemesis provoked my Julia to explore unusual and unnerving depths that I’d yet been able to portray in a film,” Dawson tells PEOPLE of working alongside Heigl.

In this exclusive photo from the film, Heigl’s character Tessa stares down Julia during a heated conversation.

“Tessa is an incredibly smart, driven woman who holds herself and those she loves to very high standards,” Heigl tells PEOPLE of her character. “Her family has been her everything since giving up her career and becoming a wife and mother so when her marriage falls apart, the world she has so carefully crafted for herself begins to unravel right along with her mind!”

In the film, Tessa begins to torment Julia in a desperate attempt to take back the life she believes was stolen from her.

“Tessa is not excited about the idea of being ‘replaced,’ ” says Dawson. “And though she seemingly does everything she can to make Julia have a smooth transition into her new life as work from home wife and loving stepmother, Tessa proceeds to intervene in subtle but effective ways to disarm Julia and destabilize her relationship and peace of mind.”

And Hiegl says playing the role of a woman who slowly comes unhinged was “liberating.”

“I really kind of loved Tessa and had a weird sort of sympathy for her. So diving into her mindset and really embracing her twisted view of things was strangely freeing,” she tells PEOPLE. “Playing a woman who will stop at nothing to get back what she thinks is hers was kind of liberating. Not caring about making everyone happy, or wanting everyone to like you, but being single-minded in getting what you want at any price? Crazy but fun!”

Unforgettable hits theaters April 21.