Were it not for the honesty, charm, and forthrightness of Ambler's own brief introduction, here's a collection that would surely not merit its cover price. Of the eight stories, six feature Dr. Jan Czissar, late of the Czech police and now a refugee in London, and Assistant Commissioner Mercer of Scotland Yard, whose murder cases the Czech intrudes on, prefacing his deductions with the grating ""Attention, please."" A Poirot-like figure, Czissar is very much a product of his times--the late 30's--brilliant, irritating, and relentlessly deducing by logic, with an arcane knowledge of poisons, body temperatures, timetables, etc. ""The Army of the Shadows,"" another wartime story, features a stranded doctor and a clique of good Germans fighting National Socialism, while the most recent story, ""The Blood Bargain,"" written in 1972, concerns a Latin American coup in which the sly Presidente escapes with his life and much of his treasure. There are glimmers here of the Ambler greatness, but, overall: slight, inconsequential fare.