Cal the Caveboy by Angela Rigley
When Cal the caveboy cannot reach the lowest branch of a nearby tree he comes up with the cunning plan of enlisting the help of a giant tortoise. However, once he is up the tree, the tortoise ambles off, leaving him stranded.
His mother asks him to help his little sister, Aggy, to find her necklace. But a rattlesnake bares its fangs at him. What should he do?