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Series / I Know This Much Is True

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I Know This Much Is True is a 2020 HBO drama miniseries based on the 1998 novel of the same name by Wally Lamb.

Ever since childhood, Dominick Birdsey has had a love/hate relationship with his identical twin brother Thomas, who has always been treated preferentially by their family due to his severe schizophrenia. His resentment is tempered by his need to protect his vulnerable twin, while viewing Thomas as a dark mirror of the fate Dominick was spared only by a fluke of genetics. As an adult, Thomas is largely able to live an independent and peaceful life with medication, but during one of his lapses, he experiences an episode of violence that lands him in a mental institution. Learning that the hospital is an unsafe environment, Dominick fights to have his brother freed, even as the incident forces him to examine his lifelong ambivalence toward both his brother and the strange, strained family that made them both what they are.

Dominick believes the key to the family's troubled history lies with his Sicilian grandfather and namesake Domenico, whose convoluted journals reveal a shocking parallel story of twins and mental illness. No matter what secrets the journals hold, the past is forever another country, and Dominick must find a way to make peace with the present by whatever means he can...until he learns that the past is a lot closer than he ever suspected, and that he has the power to make amends for a long-forgotten, shameful crime.

The series stars Mark Ruffalo in a double role (for which he won the Emmy for Outstanding Lead Actor in a Limited Series or Movie in 2020), as well as Melissa Leo, Michael Greyeyes and Juliette Lewis.


  • An Arm and a Leg: Thomas cuts off his own hand in a library as a sacrifice to stop the Gulf War.
  • Character Death: Thomas dies after he goes to the falls at night and drowns.
  • Cry into Chest: When Dominick visits Thomas at the facility, the latter begins to cry and Dominick eventually gets up and hugs him despite not being allowed to.
  • Drunk Driver: The episode ends with Dominick crashing his car into a tree after he drives around drinking beer.
  • Dying Wish: Shortly before dying, Dominick's mother begs him to promise to take care of Thomas.
  • Grief-Induced Split: As in the original novel, Dominick Birdsey and his wife Dessa divorced after their infant daughter Angela died of SIDS. They reunite at the end, with a hint they might someday become parents again. In the novel, they become adoptive parents to Joy's daughter after the woman dies of HIV.
  • Kids Are Cruel: When he was in third grade, Dominick was annoyed that a girl in his class kept lying about things like her parents' income. He lied to a teacher that the girl had been stealing from other children which resulted in the girl being suspended and eventually being missing, until her body was found by the falls.
  • Potty Failure: Thomas wets himself shortly after arriving at the forensic clinic because none of the guards listen to his pleas to let him go to the toilet.
  • Tantrum Throwing: In college, Thomas once had a breakdown when he had to write an essay and could not find a part of the typewriter that he needed, but couldn't ask Dominick because he was not there. His words to Dominick reveal that the real problem was not being able to cope with being separated from his twin brother.
  • The Reveal: Dominick finds out that Henry Drinkwater was his father, and that Ralph is his cousin.
  • Sexiness Score: In episode 3, a flashback that shows how Thomas and Dominick first met. Thomas is complaining to Dominick about "A chicks" being too arrogant so he prefers a "good-natured B chick". The waitress, a young Dessa, isn't impressed by them "scoring women". Later that night Dominick and Dessa end up meeting again when her car breaks down and we get a Call-Back to them "scoring women".
    Dominick: Uh, where do you live? Maybe my buddy and I can give you a ride home?
    Dessa: I'm not sure I'm an "A," so would I be able to go with you guys or?
    Dominick: I'm sorry, I don't grade women like... He's a... He's a weird guy.
    Dessa: Okay, okay. Yeah.
    Dominick: I'm sorry. You would be an "A" though.
    Dessa: [laughs]
    Dominick: If I was grading, but I'm not grading.
    Dessa: Okay, nice save.
  • The Show of the Books: The series is based on the book of the same by Wally Lamb.
  • Title Drop: During Dominick's monologue at the end of the episode:
    Dominick: But one day, at long last, I stumbled from the dark woods on my own and my family's and my country's past. Holding in my own hands these truths. That love grows from forgiveness. That from destruction comes renovation. That the evidence of God exists in our connections to one another. This much, at least, I figured out. I know this much is true.