Henderson's Boys 3 : Secret Army - Robert Muchamore

Britain, 1941. The government is building a secret army of intelligence agents to work undercover, gathering information and planning sabotage operations. Henderson's boys are part of that network: kids cut adrift by the war, training for the fight of their lives.

They'll have to parachute into unknown territory, travel cross-country and outsmart a bunch of adults in a daredevil exercise. In wartime Britain, anything goes.