In one of his rare performances without Bud Abbott, Lou Costello plays a delivery boy who invents a machine which turns his girlfriend into a giantess.

Professional daredevil and white-suited hero, The Great Leslie, convinces turn-of-the-century auto makers that a race from New York to Paris (westward across America, the Bering Straight and Russia) will help to promote automobile sales. Leslie’s arch-rival, the mustached and black-attired Professor Fate vows to beat Leslie to the finish line in a car of Fate’s own invention.