Mark Ruffalo Plays Troubled Twins in I Know This Much Is True Trailer

Mark Ruffalo is playing double duty in HBO’s new miniseries, I Know This Much Is True.

On Sunday, HBO dropped the first trailer for the six-part series, directed by Derek Cianfrance and based on Wally Lamb’s 1998 novel by the same name.

In the show, the Avengers: Endgame star, 52, plays identical twin brothers, Dominick and Thomas Birdsey, the latter of whom is schizophrenic.

“Your brother is seriously ill,” Rosie O’Donnell‘s character Lisa Sheffer tells Dominick.

The trailer also jumps between the Birdsey twins’ present-day life and their relationship growing up as children.

“I need you to stand up for me for once,” one of the twins tells an unknown person — and from there the trailer delves into action overdrive, with drama and tears, turning into chaos.

Melissa Leo, Archie Panjabi, Imogen Poots, Juliette Lewis and Kathryn Hahn also star in the miniseries.

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At the TV Critics Association Winter Press Tour in January, Ruffalo revealed he gained 30 lbs. for his dual role. He filmed all his scenes as Dominick for the first 15 weeks, before taking five weeks off to transform into Thomas.

Due to Thomas’ years of dependency on medication for his schizophrenia, Ruffalo said he gained weight to accurately portray the effect medications and “mood stabilizers” can have on someone’s body.

“We didn’t want it to be like I run and throw a wig on and do the same scene in the same day, so we took six weeks off to really separate these two guys,” Ruffalo explained. “And Thomas is on medication, mood stabilizers and anti-psychotics. A lot of people put on weight.”

“Putting on the weight for Thomas was really challenging,” he added. “I didn’t expect it to be. I thought I was going to have a fun time doing that, but when you’re force-feeding yourself, some of the romance of food sort of leaves.”

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The Emmy Award-winning actor also admitted he was scared to play the character of Thomas because he knew how important it was to portray him accurately and spread awareness about an “important issue.”

“It means a lot to me to be honest with that, which means going into that world and getting to know it and getting comfortable with it,” he said.

“And that’s challenging, and so that aspect of it was challenging…I was really afraid to play him,” Ruffalo added. “I think it’s really an important issue, and I want to tell it as honestly as possible. The responsibility is on me.”

I Know This Much Is True premieres April 27 on HBO.