Tom Swift's latest invention has set off an evolution revolution in reverse. His microradiation DNA scanner, destabilized by a black hole created in an earlier experiment, has created a biological time warp. Now the scanner's beam of alien energy threatens to put the entire world into prehistoric peril.

A house cat is transformed into a ferocious saber-toothed tiger...a mynah bird becomes a carnivorous flying reptile...and Tom s friend Rick devolves into a rampaging ape-man. Tom must find a way to defuse the DNA time bomb before a savage new Stone Age explodes into being!
(from the publisher)