I once had an idea for the ultimate Chicago movie. Well, at least I knew how it should end: with a wild car chase through the narrow streets of Lakeview, every vehicle -- those of the desperadoes as well as the good guys -- tuned to the Cubs' big game that afternoon. As Harry Caray bellows in the background, the lead car careers south on Kenmore, tears across Waveland, and smashes through Wrigley Field's left field wall.

It's the bottom of the ninth when this happens and two men are out. The Cubs trail but the bags are full. And it's a hit, a long one, the ball soaring high above the wall. It's the miracle long hoped for and never truly expected, a home run that will turn defeat into victory and send the Cubs to their first World Series since 1945. But the retreating Cardinals outfielder jumps onto the hood of the getaway car that  just breached the ivy, reaches the car's roof in another bound, and with his third leap hauls in the vanishing pellet.

"Holy cow!" moans Harry Caray. "What a lousy break. Boy, the Cubbies find more ways to lose . . . "

And then the camera pans the grandstand, from the left field line to the right field line, following a row of seats. And each seat is occupied by a famous actor who's come out of Chicago -- Cusack, Mahoney, Petersen, Malkovich, Murray, Allen, Metcalf, Arkin, Sinise, Frantz, Mantegna . . .  All looking more morose than surprised, for they know their Cubs. And at the far end of this procession, looking particularly unsurprised and disgusted, we see Paul Sills, and beyond Sills an empty seat. And those who understand Chicago theater will know at once that this seat represents Sills's mother, Viola Spolin, the teacher and theoretician who wrote the basic text, Improvisation for the Theater, and was, in a sense, the mother of them all.

When Harry Caray died I put the idea aside. Today there'd be even more faces to fill the seats -- Piven, Colbert, Carell, Fey -- but at the end of the row there'd be two empty seats. Paul Sills died Monday at the age of 80 at the family place in Wisconsin. The Tribune promptly posted an obit by theater critic Chris Jones, who understood that Sills was a giant. He wasn't merely present at the creation of the improvisational theater movement in Chicago -- he was the Oppenheimer who made it happen. At the University of Chicago in the late 40s, he and Mike Nichols and others created the improvisatory Compass Players -- and the vision was Sills's. A decade later he and Bernie Sahlins founded Second City. After losing interest in Second City's scripted productions, he developed "story theater," which Jones calls "the technique wherein a character could also step out of the story and serve as a third-person narrator" -- a technique that showed how "non-dramatic forms such as novels and prose could be produced effectively as drama."

I knew Sills in the early 80s when he and his family moved into a big, dilapidated house two doors up from ours on Paulina Street. The house was so astonishingly run down that Ed Zotti, the Reader contributor who lives there now, will soon publish a book on his family's epic struggle to rehab it. Ed says Paul and Carol Sills compiled a nine-page, single-spaced list of repairs they'd made -- such as jury-rigging a railing at the top of the stairs to replace the missing balustrade -- to keep the house from becoming a death trap for themselves and their four daughters. Despite all their efforts, the Sillses barely made a dent. I enjoyed the house because it spoke so well of its occupants. Only geniuses and free spirits, I felt, could live in such a place and think, "So, what of it?"

But I'd never call Paul Sills blithe. His wife Carol was very friendly. Neva, their youngest daughter, joined a play group our oldest daughter was in. She was lively and full of mischief. But Paul was moody. He'd moved back to Chicago to teach and create a new company, but the work didn't go that well and a couple of years later the family moved on. Paul was friendly enough, but he didn't say much and he wasn't warm. I have a lingering impression of a man in a red plaid shirt moving at a fast clip up the sidewalk, impatiently thinking complicated thoughts. As a brooding young man at the University of Chicago plotting the future of theater he probably cut the same sort of figure as the nuclear physicists who'd been around campus a few years before splitting the atom -- someone with little regard for appearances but a high regard for his own worth, preoccupied by theoretical concerns the rest of the world couldn't be expected to understand, and fiercely determined to get to the core of things, to Truth.

UPDATE: For more on Paul Sills, including links to commemorations by Second City, WBEZ, and the Chicago Improv Festival, please visit the Reader's new theater blog, Onstage .