A short, exciting novel about Danny and Lally - adopted because their birth mother couldn't look after them. They are worried because their parents are having a baby of their own. A running theme throughout the book is their concern that they won't be 'the specials' any more. Having been sent to stay with their Aunt Isabel while the baby is coming, they have an adventure with two palaeontologists who are looking for signs of dinosaurs in the valley. One of them (the nice one - Celia) tells them she is adopted too, and they trust her with their secret find - stones with dinosaur footprints. The children and Celia thwart the villain, who is out to prove the existence of the dinosaurs for his own selfish ends. The children's parents appear at the end of the story, complete with new baby sister, and all ends happily. Good, old-fashioned adventure.