It's 1944 and Florence is a talented engineer in the Women's Auxiliary Air Force patching up planes to make sure that the brave Spitfire pilots of Cottisbourne airbase return safely day after day. When she befriends the new squadron leader - shy handsome Siegfried - it seems that romance might blossom under the war-torn skies. But Florence is nursing a broken heart and a terrible secret which might destroy her one chance of happiness . . . Meanwhile a new plane is being developed that could turn the tide of the war but Florence fears there is traitor is in their midst putting Siegfried - and the whole country - in terrible danger. Can Florence save her Spitfire boys and her own heart?