As part of an Anzac Day project at school, Matthew has to find out if any of his family members fought during World War II. His grandmother tells him of his Great-great Uncle Lennie, who was in the Air Force. Matthew learns that Lennie was one of 617 Squadron, the Dambusters, trained for a special mission. Sent to drop specially designed bombs on to the Moehne, Eder and Sorpe dams in the Ruhr industrial valley in Germany, the squadron faced many dangers and that only nine of the eighteen Lancasters sent on the mission returned to England, and 56 airmen lost their lives during the dam-busting raid.