Superintendent Macdonald, C.I.D., studied his fellow-passengers on the Vienna plane simply because he couldn't help it, because he hadn't conditioned himself to being on holiday. The distinguished industrialist he recognised: the stout man he put down (quite mistakenly) as a traveller in whisky. The fair girl was going to a job (he was right there) and the aggressive young man in the camel coat might be something bookish. Macdonald turned away from his fellow-passengers deliberately; they weren't his business, he was on holiday - or so he thought. Against the background of beautiful Vienna, with its enchanting palaces and gardens, its disenchanted back-streets and derelicts of war, E. C. R. Lorac constructs another great detective story with all its complexities, an exciting and puzzling crime story.