Having a booze-up with a bunch of his old fly-buddies, former Royal Air Force pilot Mark Stevens, an American, gets into an altercation with one of them who goes out of his way to be insulting. They patch things up, and get on with their drinking. Next morning (or rather afternoon), Stevens wakes up in a strange hotel room only to read the headlines that the other guy has been murdered. But he can't remember a thing, having been slipped a Mickey the night before.
This is Cornell Woolrich territory, though he didn't have a thing to do with it. With Scotland Yard on his tail, Stevens races against time to retrace his vanished footsteps and find the real killer. Staunchly by his side is a fiancée Jean Kent; her opposite number is temptress Dianne Foster, available wife of another of the carousers. In his investigations, Stevens finds that some of the wartime heroes have, in the post-war years, taken to less heroic pursuits, running a phony import-export racket his inopportune sleuthing threatens to expose....
The Lost Hours (a.k.a. The Big Frame) is little more than a British crime programmer, but it's briskly done and keeps you awake. And despite the London landscape and the recurrent `I say, see here, old boy's that strew the dialog, its themes and story line place it neatly in `The American Style' of film noir.