Modern-day eight-year-old Barney (Grant Ashley Warnock) meets Stig (Keith Jayne) – a boy from prehistoric times living in a cave in chalk pits that are used as a rubbish dump.
Barney and Stig quickly become friends and learn to communicate with each other without language, as Stig speaks no English.
Barney helps Stig and the two spend time repairing and beautifying Stig’s den.
On one occasion, Barney is cornered by the bullying Snarget brothers, who become uncharacteristically docile when Stig appears. Although Barney mentions Stig to others, no one (except the Snargets) believes that Stig is real.
During a very hot and humid mid-summer night, when Barney and his sister Lou (Janine Tidman) cannot sleep, they find themselves transported back in time and out onto the Downs.
To their surprise, they meet Stig, back with his own people, engaged in constructing four gigantic standing stones. They spend a night camping out with the people of Stig’s tribe and helping to shift the final stone into position before sunrise.
