Not much to say about tis rather routine, short, pre-war espionage drama. Roger Livesey is an aeronautical engineer working with his team (Basil Bradford and Barry Barnes) on a top secret design for a test aircraft. Meantime Felix Aylmer ("Col. Cairns") is in charge of security and when he suspects the plans are being copied we have to try and suss out who the traitor is - and discover it's not just the nation that might be being betrayed. It's got an efficient script, the story doesn't hang about and there is some enjoyable aerial photography (interspersed with some rather fun toy aircraft-on-a-wire type shots too) with quite a good ending. David MacDonald does fine with what must have been a tiny budget, and it has a certain, enjoyable, generosity of spirit about it.