Over the next several months they sat with him, accepted him as a member of the tribe, and encouraged his mission to improve the world at face value. And save his life they probably did, in part by suggesting that he seek help.

It was Ms. Holley who delivered the message. “I trusted her completely, so when she said I was hallucinating — when she used the word ‘hallucination’ — I knew it was true,” Mr. Greek said. “I would have to give the medication another try.”

He was lucky. It worked, blunting the psychosis enough that he was able to complete a programming course and find work, first in Illinois and later back in Athens at Ohio University’s Information Technology department. In time he found something more: During a snowstorm in 1996, Mr. Greek knocked on the door of a neighbor he had seen around Athens, a single mother with two teenage children, carrying a full-time job plus graduate classes, who was at that very moment (he would learn later) praying for something to get her through the winter.

The man at the door did not exactly look like a savior, in his beat-up jeans and unruly hair, his soft eyes and half-smile. But he offered to cook dinner — stir fry — on a day when the fridge was nearly empty.

The two neighbors became friendly, then close, and finally fell for each other. Neither can say exactly when it happened, but she remembers looking out her window one day to see Mr. Greek pull up to his apartment across the street, his old Honda coughing white smoke. He popped the hood and backed away from the car in slow motion, staring at the engine, then turned abruptly toward his apartment — and vanished, falling face-first into some bushes. “I thought, ‘Well, O.K., he’s got something,” she said. “I’m not sure what. Absentmindedness, maybe?”

They married in 2003 (Mr. Greek’s wife, an artist, asked that her name not appear in this article, for her own privacy), and she helped him fit his religious delusions, now controlled by medication, into a coherent personal story that has guided his day-do-day life.

The frightening voices and ominous signs saying that he was damned were no more than embodiments of his very real childhood terror of being cast out, as the schoolyard boys threatened. His search for heaven on earth was in part an attempt to escape that fate, to find a secure place. But it also dramatized a longing to put the world right, a mission that may have started as vain fantasy, but in time became an emotional imperative, a need to commit small acts of kindness, like cooking dinner for a snowed-in neighbor.