A plate-glass window and a sudden gust of wind christened Paul Mullin's career as a playwright. It was 1990 in New York City, and Mullin was 23, working as a window washer. "It was the stupidity of youth times a thousand," he says, sitting in the backyard of his Seattle home with a glass of bourbon, soaking his feet in his sons' inflatable pool. "I was also working as an actor at the time, and as a night porter, so during the day I was climbing 60-story buildings on two hours' sleep. Stupid."

Hours before the opening of his Ellison and Eden, Mullin was in a fancy apartment building, cleaning its 70-pound windows. He had to pop each one out of its frame and lean outside while he washed the glass. He was struggling to yank one of the windows back into its frame and called Al, the large Puerto Rican building manager, to help. A rogue gust blew the window into Mullin, shattering it against his face and body.

"I asked, 'How bad is it, Al?' And he just stood there freaking out, going 'uh—uh—uh.'" Blood was pouring out of Mullin's face, but he felt oddly calm: He knew he had to get to a hospital immediately. Fortunately, there was an emergency room kitty-corner from the apartment building. "Cars were beeping at me as I tried to cross the street, and I thought: 'So this is how it is? My face is bleeding and you're honking? Fine.' That's when I decided to leave New York."

He got 40 stitches sewed into his cheek that night and missed the opening of Ellison and Edison. "We were a young, angry ensemble," Mullin says. "Our artistic director—and main donor—was a call girl."

Eighteen years, 18 productions, two marriages, and two children later, Mullin is still angry. He writes bellicose letters to artistic directors and critics. He rails against regional theaters ("it's all based on a high-school drama- club mentality"), actors' unions ("I scab and happily encourage others to scab"), and himself ("I am in the same shape as theater in general—I don't have a fucking clue").

But his anger is focused and generative, an anger that makes things happen: "We're all going to be dead soon," he says as night falls in his backyard. "And we're never going to feel properly compensated for it. So just do the work. Just do it." He finishes his bourbon. "Want another?"

Mullin was born in Jacksonville, Maryland, to a family he describes as "shanty Irish from the wrong side of the tracks." His people were poor, tough, and alcoholic. (Mullin's father died before he was born, drunk behind the wheel.) He studied theater at the University of Maryland and got his actors' union card at Ford's Theatre, playing Young Scrooge during a production of A Christmas Carol. He took naps in the box beneath the one where Lincoln was assassinated. "You couldn't nap in that box," he says. "It was cordoned off. Besides, that'd be fucking disrespectful."

Mullin's conversation is fast, passionate, and occasionally bruising—it is easy to imagine him as a Tammany Hall politician. "I know everyone and I forget nothing," he says, recalling a story of an actor who abandoned one of his fringe productions for a union job and who, years later, came asking to be in one of Mullin's plays. Mullin wouldn't even let him audition.

Mullin's characters tend to be as tough and smart as he is. Louis Slotin Sonata—his masterpiece, based on a true story—begins in a laboratory in Los Alamos, where physicist Louis Slotin is showboating. He's performing a "criticality test," putting two half-spheres of beryllium around a plutonium bomb core and measuring the neutron collisions. The test is so dangerous, they call it "tickling the dragon's tail." The spheres of beryllium must come close but never touch—if they do, the core will react and send a prompt, fatal burst of radiation through the room. Slotin keeps the halves separate with the blade of a screwdriver, twisting it back and forth. Of course, the blade slips and Slotin becomes a walking dead man, with nine days left to live.

That opening scene is typical of Mullin's best work: a polychromatic marvel of science, comedy, and sadness. In eight pages, he whisks the audience across an astonishing stretch of ground, explaining how nuclear bombs work, a brief history of the Manhattan Project, the fraught relationship between the military and its scientists, machismo in the lab, and his charmingly arrogant protagonist. (Slotin calls himself the "chief bomb putter-togetherer" and mocks the bureaucratic pomposity of his military employers by describing wood blocks as "Custom-Made Pajarito Canyon Criticality Contraption Safety Prototypes One and Two.") Exposition was never so entertaining.

The play fractures along with Slotin's decaying mind. From his hospital bed, Slotin talks physics with his friends, biology with his doctors, Yiddish with his father, and sex with a cute nurse. By the end, Slotin is bantering with the dead, performing a musical number as Dr. Josef Mengele, and tickling the dragon's tail with the Lord.

Until the Alfred P. Sloan Fountain gave him some money to produce Louis Slotin Sonata in New York, Mullin never thought of himself as a "science playwright." Which is odd, since special topics in science and technology drive much of his work: Louis Slotin Sonata (nuclear physics and radiation sickness), Tuesday (a kind of amnesia called Korsakoff's syndrome), The Septarchy (quantum physics and artificial intelligence), and The Ten Thousand Things (time and the real-life attempt to build a clock that will last 10,000 years).

"My wife says I'm fascinated by the questions that keep sophomore college students up and smoking weed all night. The question in Tuesday is: 'What if, maaaaan, you were an amnesiac who just remembered everything, and it turns out you were a dick?'" Which is exactly what happens to Audie McCall, an alcoholic junk-bond trader who barely survives a catastrophic car wreck. He wakes up each morning as a tabula rasa. By bedtime, he's remembered he used to be an abusive, neglectful monster. Watching Tuesday is like waking from one of those dreams where you've done something horrible and, through the haze of fresh consciousness, you slowly and blessedly realize it was only a dream. Tuesday is like that, except the other way around. For Audie, every day is a fresh horror.

Mullin's plays keep a delicate tension between the intellectual and the human—they are cerebral, but warm-blooded. His plays explore not just ideas but the effects of ideas. Mullin is, essentially, a gnostic playwright, drawing out the drama behind the discovery, the comedy behind the theory, and the knowledge behind the knowledge.