Allied spies and Nazi Agents insinuate themselves at a Scottish cottage (converted to a wartime hospital) with interests on an inventor's nearly perfected bomb sight.
Leslie Banks
as John Barrington
Jeanne De Casalis
as Mrs. Barrington
Carla Lehmann
as Helen Barrington (as Carla Lehman)
Alastair Sim
as Charles Dimble
John Mills
as Flt·Lieut. Perry
George Cole
as Ronald
Michael Wilding
as Alan Trently
Frank Cellier
as John Forest
Muriel Aked
as Miss Fernery
Wally Patch
as Evans
Muriel George
as Mrs. Trimm
Hay Petrie
as Dr. Truscott
