There were two Peter Lorre films that made a big impression on me growing up, on was The Beast With Five Fingers, the other was The Mask Of Dimitrios. It was such a journey thrhugh the seamy underbelly of pre-war Europe, it was utterly enthralling. I'm pretty sure I read the book, but I can't remember so it must have been long ago. It is, obviously, classic Ambler, in a class all his own as an academic-turned-whodunit-author becomes obsessed with the life of a dead criminal he views, by chance, in a Turkish secret poilce morgue.