Release Message:  The story of a boy named Bob Miller whose scientist father, Sam Miller, has invented a "time ring", a circular device that allows time travel. Written by Lester Del Rey.

Description:  The novel tells the story of a boy named Bob Miller whose scientist father, Sam Miller, has invented a "time ring", a circular device that allows time travel. Bob, his friend and his friend's father ("Doc Tom", an archaeologist) travel through time in search of Bob's father, who has disappeared while traveling alone. Beginning in the Mesozoic Era (Sam's planned destination), the story depicts various adventures while the travelers jump from point to point in Earth's prehistory in search of the missing scientist.