To play Saul Berenson, he has drawn on all his highs and lows. He also met with a former C.I.A. agent and his two grown daughters to discuss their lives growing up. “What I’m interested in is an emotional system,” he said. “When were you afraid? Why? Did you pray? Shake? Sweat? The way I like to work is to attach personal experiences to what I’m doing, so it helps tremendously if I can write my own play under what the writer has written. Saul’s heart is in his head. He dreams for the greater good of the world. Saul is now 60 years old, as I am, and he has had a full life in his business, as I have, and he doesn’t know how long he gets to be around, as I don’t. He recognizes the gift of youth personified by his child in this piece, who is Carrie. He believes that both the savantlike and intellectual qualities of Carrie’s nature are the greatest single hope for humanity. He believes so deeply in her possibilities.”

The more I spoke with Patinkin about his own father, the more it seemed he was channeling the man, whom he loved deeply. Lester Patinkin died when his son was 19. Saul’s decency, intellect, compassion and hidden demons seem to resonate with Patinkin’s memories of his father even as the characterization seems something like a wish — to create a man he never had the chance to know better.

Lester ran People’s Iron and Metal Company, a Chicago-based junk business, founded by his father, Max. The defining event in his life was a diving accident he suffered at 20, breaking his neck in Lake Michigan. “A few years later during World War II, he was in San Antonio,” Patinkin said, “and the tube that brings the spinal fluid to the brain was closing from this neck injury. He was having these tremendous headaches, and they were going to have to insert a fake tube. It was a primitive operation, and during the surgery, they touched the wrong thing, so my father was paralyzed for three years. He teaches himself how to walk and talk. He comes home, and days later the girl he was engaged to, who he was in love with, her mother said: ‘He’s damaged goods. Let him go.’ ”

Eventually, Lester married Doralee Sinton, and they had a daughter, Marsha, then Mandy. In spite of his efforts at rehabilitation, Lester was physically compromised for the rest of his life. “If you’d say, ‘What was your father’s greatest pain?’ it’s that he couldn’t play catch with me because he couldn’t control his right hand,” Patinkin recalled. “He was worried that he would throw the ball too hard and too fast and he’d hurt me. I remember when my aunts and uncles would say, ‘You don’t know your father,’ meaning before the brain accident. My little kid-ness was going, ‘What do you mean I didn’t know my father?’ He was a great man. He taught himself how to walk again, to write with his left hand. My father was a hero.”

When Lester became ill with cancer, his wife and his relatives decided to tell him he had hepatitis instead. “Cancer was a death sentence then,” Patinkin said. “I’m instructed to follow these orders, so I’m never able to talk the truth to my father at the end.” Patinkin grew teary. “He did his own research and was clearly cognizant of the fact that none of the pieces fit,” he went on. “It just destroyed me. I was forced to lie to my father by doctors and relatives. I made that choice and agreed with them, and I will never, ever get over it. If I hear a lie in my life with my children, with my wife, my work, my audiences, I want to annihilate myself, vaporize myself and wipe myself off the face of the earth.” He mopped the sweat from his face. “Never again will I subject myself to not trying my damnedest to tell the truth. That’s my gift and my curse.”

Now that Patinkin’s mother is 88, the two are able to discuss that period. “We talk about the struggles we went through, the mistakes we made as parents,” he said. “Because with all love toward my mother, I heard her being critical of my father, relatives, friends. My father was the quiet one in the family, he was passive, whether it was his nature or what happened with his injury, I will never know. But my mother was the voice, she had to run the show. I have the strength from my mother, the survivability. I have wonderful qualities from my mother — but please, Mother, forgive me — I heard judgment constantly about my father. She questioned him enjoying investing in the stock market, little investing, he wasn’t rich, buying the kids AT&T. I just heard the voice saying, ‘Not good enough, not good enough, not good enough.’ ”

Even though Patinkin stresses that his mother always supported his career choice, he still had trouble hearing direction as something other than criticism. “I struggled with letting in other people’s opinions,” he said. “During ‘Chicago Hope,’ I never let directors talk to me, because I was so spoiled. I started off with people like Milos Forman, Sidney Lumet, James Lapine, unbelievably gifted people. So there I was saying, ‘Don’t talk to me, I don’t want your opinion.’ I behaved abominably. I don’t care if my work was good or if I got an award for it. I’m not proud of how I was then, and it pained me.”