Cuckoo (2012)

WWII, 1942. Losses over enemy territory of planes from RAF Bandon - call-sign "Dunnock" - a British bomber airbase in Southern England, have its C.O. concerned. For Wing Commander Marshall, the numbers of his bombers being intercepted are high... consistently too high to be a fluke. His suspicions that all is not what it seems among the base staff are realized when Intelligence Office Lt. Larry Ford confirms transmissions to German High Command are being detected, originating from somewhere in the base. Who is the traitorous cuckoo in the nest? And can they be found before more lives are lost?