Clean-cut Guy Farrar is sent by his uncle, the old spymaster, to determine who is stealing information from the remote island aerodrome where a plane is being built that will give Great Britain the edge in the difficult years between the wars. There's double-dealing, kidnapping, attempted murder, and nefarious double agents, so it's hard for Guy to know who he can trust. He's not even sure of Joyce Gurney, even though he's falling in love with her.