Dermot Mulroney is out for vengeance.

In the new revenge thriller Ruthless, the My Best Friend's Wedding star plays Harry, a high school wrestling coach mourning the death of his daughter, who was murdered under mysterious circumstances. "Harry's daughter was murdered four years ago. Some scumbag drugged her, raped her, and left her to die in a ditch," a character explains in the new trailer, which EW is exclusively debuting, above. "I think he's trying to keep that from happening to your daughter."

As the trailer progresses, we see how Harry's grief compels him to take matters into his own hands when he sees other women being abused. After observing signs of abuse in one of his students, Harry visits her house at night to knock some sense into her father. "Stop hitting that kid," he says. "I think you oughta mind your own business, coachy," the father responds.

"Before I leave tonight, I'm definitely breaking your right arm," Harry says before brutally attacking the abuser. "See you at school, kiddo," he nonchalantly mutters to his student as he walks out the door.

Later, Harry learns of a crew "known for trafficking girls across state lines," and we see him come to blows with a number of enemies, presumably with connections to the human trafficking ring — including Lost's Jeff Fahey, who appears to be one of the leaders of the organization.

Harry continues his quest even after a police officer asks him to cease his vigilante work. "I don't care if I spend the rest of my life in prison," Harry says. "I'm gonna kill them."

Ruthless — available Dec. 15 on digital and VOD — also stars Melissa Diaz, Mauricio Mendoza, Tonantzin Esparza, and Niko Foster. Watch the full trailer above.

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