This exciting mystery story will keep readers gripped, as brothers Joe and Carl quickly realise it’s not always best to keep what you find. Written by Alan Durant. Collins Big Cat Progress books are specifically designed for children at Key Stage 2 who have a Key Stage 1 reading level, giving them age-appropriate texts that they can read, building their confidence and fostering positive attitudes towards reading.Text type: A mystery storyCurriculum links: P.E.