Who’s Who in HBO's I Know This Much is True

Based on Wally Lamb’s 1998 novel of the same name, HBO’s I Know This Much is True follows the efforts of a middle-aged man to get his paranoid schizophrenic twin brother released from an asylum. Blue Valentine and Place Beyond the Pines filmmaker Derek Cianfrance wrote and directed the six-episode adaptation, which promises to be a stirring original drama.

Premiering this Sunday, the miniseries revolves around a core ensemble of recognizable faces, staring with Mark Ruffalo, who will be playing not just one, but two roles in the series.

Mark Ruffalo as Dominick and Thomas Birdsey

Mark Ruffalo may be best-known for his work as Bruce Banner/The Hulk in the Avengers franchise, but his career extends far past the limits of the Marvel Cinematic Universe. First garnering critical acclaim for his performance in Kenneth Lonergan’s 2000 drama You Can Count on Me, Ruffalo went on to star in a number of popular dramas and comedies, including 13 Going on 30, Eternal Sunshine of the Spotless Mind, Collateral, Zodiac, Shutter Island, Now You See Me, and Begin Again. Ruffalo has also been nominated for an Academy Award a total of three times, for his performances in Foxcatcher, The Kids Are Alright, and Spotlight. In I Know This Much is True, he plays both Dominick Birdsey and his paranoid schizophrenic twin brother, Thomas. It is the first time he's recurred in a TV series since his work on the short-lived 2000 cop series, The Beat.

Kathryn Hahn as Dessa Constantine

We here at Primetimer have crowned her "the queen of Peak TV," and for good reason. Following her recurring work as Lily Lebowski on NBC’s Crossing Jordan, Hahn has become one of the busiest TV actresses working today. She’s had lead roles in Mrs. Fletcher, I Love Dick, and Happyish, and has — perhaps even more notably — turned in memorable guest and supporting performances on shows like Parks and Recreation, Transparent, Girls, The Kroll Show, and Bob’s Burgers. She plays Dessa Constantine, Dominick’s ex-wife, in I Know This Much is True.

Rosie O'Donnell as Lisa Sheffer

Rosie O’Donnell has been a film and TV star since the early 1990s, when she made her film debut in the comedy classic, A League of Their Own. From there, O’Donnell appeared in Sleepless in Seattle, The Flintstones, Beautiful Girls, and Disney’s Tarzan. More recently, she starred as Tutu in the Showtime comedy, SMILF, and has had guest roles on The Fosters, Mom, Difficult People, and American Dad. O’Donnell is also famous for her work as a stand-up comedian, her daytime talk show, The Rosie O'Donnell Show, which ran from 1996 to 2002, and for her 2 stints as a host on The View. In I Know This Much is True, she plays Lisa Sheffer, a social worker at the institute where Thomas is staying.

Melissa Leo as Ma

Melissa Leo’s screen career has seen her go all the way from a 4-year-run on All My Children in the mid-to-late 1980s to an Oscar win in 2011 for her performance in The Fighter. In between those two milestones, Leo turned in a number of memorable performances on TV, including her recurring role as Kay Howard on Homicide: Life on the Streets and her turn as Toni Bernette on HBO’s Treme. Since her Oscar win, Leo has starred in films like Flight, Prisoners, The Equalizer, Snowden, and The Equalizer 2, and had recurring roles on both Wayward Pines and the Showtime dramedy, I’m Dying Up Here. She plays Thomas and Dominick’s mother, Concettina Ipolita Tempesta Birdsey in I Know This Much is True.

Juliette Lewis as Nedra Frank

Juliette Lewis followed her breakout turn as Audrey in 1989’s National Lampoon's Christmas Vacation with one of the best runs of any actress in the 1990s. She kicked the decade off with the Martin Scorsese-directed Cape Fear, for which she received a Best Supporting Actress nomination, and followed that up with roles in Husbands and Wives, What’s Eating Gilbert Grape, The Basketball Diaries, Strange Days, and From Dusk Till Dawn. Perhaps her most well-remembered performance came when she played the crazed Mallory Knox in Oliver Stone’s Natural Born Killers. Lewis has had several TV roles of late, appearing on shows like Secrets and Lies, Camping, The Conners, and Sacred Lies. I Know This Much is True sees her playing Nedra Frank, a self-absorbed grad student hired by Ruffalo’s Dominick.

Archie Panjabi as Dr. Patel

Archie Panjabi is having a particularly busy 2020. Not only is she playing Dr. Patel, Thomas’ latest psychologist, in I Know This Much is True, but she is also currently starring in another HBO series, Run. Panjabi won an Emmy and was nominated another two times for her performance as Kalinda Sharma on The Good Wife, and has had recurring roles on others shows like The Fall, Next of Kin, Blindspot, and Departure.

Imogen Poots as Joy Hanks

Imogen Poots has carved out a successful film career for herself in the 13 years since her first notable screen role as Tammy in Danny Boyle’s 28 Weeks Later. This writer will always remember her best for her performance as Amber in the 2016 horror-thriller, Green Room, but some of her other notable film credits include Fright Night, That Awkward Moment, Need for Speed, Popstar: Never Stop Never Stopping, and The Art of Self-Defense. She most recently appeared in the 2019 remake of Black Christmas. Her other TV credits include the 2010 British mini-series Bouquet of Barbed Wire, and a lead role in the short-lived Showtime series Roadies.

Bruce Greenwood as Dr. Hume

Playing Dr. Hume in I Know This Much is True is none other than Bruce Greenwood. A screen actor for over 40 years, viewers will likely remember Greenwood best for his performance as Captain Pike in the J.J. Abrams-directed Star Trek films, or for his role as Randolph Bell on FOX’s The Resident, but those roles don’t even begin to hint at the true breadth of Greenwood’s career. He's appeared in popular films like Gerald’s Game, Flight, I, Robot, and Thirteen Days, while his most notable TV credits include roles on St. Elsewhere, Mad Men, The River, and American Crime Story. I Know This Much is True marks the second collaboration between Greenwood and series director, Derek Cianfrance, following Greenwood’s work in Cianfrance’s 2013 film The Place Beyond the Pines.

Michael Greyeyes as Ralph Drinkwater

The premiere of I Know This Much is True caps a busy few months for Michael Greyeyes. This past December, the actor appeared in both the Netflix original series, V Wars, and the Disney+ film, Togo, before appearing in a recurring role in the Apple TV+ series Home Before Dark. Viewers will probably also remember Greyeyes for his turn as Qaletaqa Walker on AMC’s Fear the Walking Dead, or for his haunting performance as Brett Woodard in the third season of HBO’s True Detective. He plays Ralph Drinkwater in I Know This Much is True.

I Know This Much is True premieres on HBO this Sunday, May 10th at 9:00 PM ET.

People are talking about I Know This Much is True in our forums. Join the conversation.

Alex Welch has written about television and film for TV by the Numbers, IGN, The Berrics, Paste Magazine, Screen Rant and GeekNation. Follow him on Twitter @alexrwelch.