The Stone Age clash

Twins, Scarlett and Thomas, are learning about the Stone Age at school. Grandad offers to use his time machine to send them there. Thomas wants to see a sabre-toothed tiger; Scarlett wants to see Stonehenge, but they were thousands of years apart, what should they do? Go back twice of course! The twins have travelled back in time to 40,000 years ago! They must survive in the forest with the help of their new homo-sapiens and Neanderthal friends. A sabre-toothed tiger is nearby and so are the huge woolly mammoths. Then, they travel back to 5,000 years ago. Scarlett is in danger, she's landed in the sacred site of Stonehenge and angered the antlered priest, will he sacrifice her at dawn? Thomas has joined the young men who are pulling the first enormous stone to Stonehenge.