Y"ou are about to witness the most sense-confounding drama on the stage today," the tall, goateed man bellows to a packed auditorium in Oshkosh, Wis. "Thirty-six inches of solid steel blade turning at 2,000 revolutions per minute will cut through lumber like a hot knife through butter. I can assure you, anything or anyone placed beneath it would have the same thing done to it"—or her.

Harry Blackstone Jr., 44, is really saying: "Ladies and gentleman, I am about to saw my wife in half." It is only an illusion, of course, despite the whining blade and sawdust, but Gay Blackstone, 30, the sawee, still is not wild about it. Especially since she also gets shot from a cannon, turned into a tiger, levitated and subjected to countless other indignities in the course of the show. Fortunately, the Blackstones have two formal agreements in their five-year-old marriage: (1) never to go to bed angry with each other and (2) never to go onstage angry with each other.

Their commitment is now being thoroughly tested, for they are barely a month into a cross-country tour that will take them to 110 cities in 27 states by March. Blackstone's show—it travels with a moving van full of equipment, two buses and a menagerie vehicle for such co-stars as Sebastian the jackass, Misty the 6,500-pound elephant and Bolma the Bengal tiger—is probably the most ambitious since the spectacles mounted by Harry's late father, the Babe Ruth of magic, in the 1940s. "I am responsible for the livelihood of 29 people," proclaims Blackstone, who rarely drops his ornate onstage diction even when asking the time. "I think I will succeed and my confidence is not unfounded."

He has the active support of third wife Gay, who not only plays foil but also co-produces the extravaganza. A close friend says the Blackstones are "two personalities working toward the same goal—they're busy, hectic and overbearing." But the consensus is that they're good bosses to work for considering the pressure. Gay professes to have no problem accepting second billing. "I had so many friends who were so unhappy trying to be stars," she says. "I love to perform but I don't have to be a star."

Originally she had more showbiz ambition than Harry. While he had made his stage debut at six months in his father's act, he later had qualms about picking up the wand when Harry Sr. passed it on: "I thought one legend in a household was enough." Inevitably, he learned the tricks of his father's trade, but after finishing high school at 15 (his childhood friends included future playboys Peter Revson and Lance Reventlow), he graduated from Swarthmore, then studied theater arts at Southern Cal and the U of Texas before enlisting in the Army. His father, who once pickpocketed a presidential bodyguard's revolver while performing for Calvin Coolidge, lost a multimillion-dollar fortune during the Depression. So after being mustered out, Harry Jr. edged back into show business, first as an announcer at the Lyndon Johnsons' TV and radio station in Austin, then as a manager for West Coast companies of Hair and associate producer of the Smothers Brothers TV show. Finally, at Tom Smothers' urging, Harry returned to performing on television and the international club circuit seven years ago.

He was hardly struggling then, but, says a friend, "Before Gay, Harry had a one-man show. Now he has an act. She is the dynamo." Harry had been married twice and was in the process of a divorce from his second wife in 1970 when he hired Gay to work as his assistant in a show sponsored by the Magic Castle in L.A. After growing up in the South, Gay attended five colleges from Texas Christian to California State (L.A.) with notions of becoming a ballet dancer. Then she toured with Bob Hope's USO show and spent a year as one of Dean Martin's TV Gold-diggers. (Her spot was on the far right of the line; at the far left in those days was Goldie Hawn.)

Gay wasn't overwhelmed with offers after she left Dino, but the name of Blackstone didn't exactly knock her over. "I was almost fired as soon as I took the job," she recalls. "I didn't want to work for a magician." But familiarity soon dispelled contempt and three years later they were wed. "Our previous marriages taught us what a person can take and what he or she can't," says Gay, whose own first marriage ended in divorce. "They also made us more tolerant."

Once he began performing again, Harry had his name ("It opens a lot of doors, but they're on springs since people expect a lot") and a repertoire of 90 illusions that helped him live up to it. In 1976 he was named the official "Bicentennial Magician." Then in 1977 he gave a command performance for Queen Elizabeth's Silver Jubilee, and this year peers voted him the coveted Star of Magic, only the 11th bestowed in the 80-year history of the Magic Association. Harry has already starred in three TV specials and plays an evil magician in a just-finished Universal TV movie based on the Mandrake comic strip. He would like to have his own Broadway vehicle or TV series.

The current tour has caused an enforced separation from Harry's four children from his previous marriages. Tracey, 10, Adrienne, 11 (the most promising magician in the family, Dad says), and Cynthia, 15, all live at the Blackstone home in Redlands, Calif., with a grandmother and a maid, though they often join the tour on holidays. Harry III, 20, is studying in California's Orange Coast College. "The kids are independent little people," says Gay.

She and Harry cope all right, too. Their new $190,000 bus comes equipped with a private suite and a sauna. Gay complains that it takes her four hours to wind down after a show and she wants a Jacuzzi to help her insomnia. Blackstone, however, requires only a matter of seconds to transform himself into a sawing-away, sleeping person.