Katherine Heigl Has It Out for Rosario Dawson in Stirring 'Unforgettable' First Look

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Katherine Heigl might be known for her romantic comedies, but her next big-screen outing leans more towards Fatal Attraction.

ET has a first look at the Emmy winner in the upcoming thriller, Unforgettable, in which Heigl has a knock-down-drag-out battle with co-star Rosario Dawson.

PICS: Katherine Heigl and Josh Kelley Celebrate Holiday-Themed Baby Shower Ahead of Baby No. 3's Christmas Arrival!

The film follows Tessa Connover (Heigl), who is barely coping with the end of her marriage when her ex-husband, David (Geoff Stults), becomes happily engaged to Julia Banks (Dawson). As Tessa watches Julia move into the life she once shared -- including raising her daughter, Lilly (Isabella Rice) -- Tessa sets on a mission to make Julia's life a living nightmare.

"You know there was a time when I thought we were on the road to getting back together, but then he met you," Heigl's jealous character says in the trailer.

Original Charlie's Angels star Cheryl Ladd plays Heigl's mom in the movie, and she gushed to People recently about the "great time" she had working with Heigl on the film.

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Ladd described The Ugly Truth star as "absolutely adorable, darling, and wonderful to work with."

"I had a great time with her," she said.

Heigl shot the movie before she became pregnant with baby No. 3. She and husband Josh Kelley, who are already parents to daughters Nancy, 8, and Adalaide, 4, celebrated at a mountain-themed baby shower.

WATCH: Katherine Heigl Shares Sweet Photo of Her Bare Baby Bump

"My mother very graciously threw Josh and I the most beautiful and celebratory baby shower last weekend," Heigl wrote on her blog, Those Heavenly Days, on Saturday. "She asked me for some direction on the décor and the vibe I was hoping for, so I headed straight to Pinterest to cultivate a look for the shower that spoke to not only the holidays, but also our mountain home in Utah, where the baby will be born."

Unforgettable hits theaters April 21, 2017.