The Sleepwalker, 9

Teen special agents investigate a deadly plane crash in the ninth book of the CHERUB series, which Rick Riordan says has "plenty of action." CHERUB agents are highly trained, extremely talented--and all under the age of seventeen. For official purposes, these agents do not exist. They are sent out on missions to spy on terrorists, hack into crucial documents, and gather intel on global threats--all without gadgets or weapons. It is an extremely dangerous job, but these agents have one crucial advantage: Adults never suspect that teens are spying on them. In The Sleepwalker, a commercial plane explodes over the Atlantic Ocean leaving 345 people dead. Crash investigators suspect terrorism, but they aren't getting anywhere. But when a distressed twelve-year-old calls a police hotline and blames his father for the explosion, James Adams and his sister Lauren are assigned to befriend the boy to find out the shocking truth...