Computer specialist Tom Baxter is developing the hardware and programs to control an unmanned exploratory probe vessel. But something goes very wrong, and Tom and his girlfriend, Karen Jordan, suddenly find themselves in another universe, and can't find their way back home. Their only chance of returning is to travel from universe to universe, hoping desperately to find trends that might lead them back home. In their travels they discover that other universes have many startling similarities, and also many differences. They also discover unexpected things about each other, and about...