Crime & Co. — S. Fowler Wright

When Bulfwin is found murdered in his office, the prime suspect becomes his American partner, Kingsley Starr, who admits having visited the man on the night of his death. But then the coroner finds that Bulfwin had been murdered by two DIFFERENT guns fired by two DIFFERENT men at exactly the same time. Who really killed Bulfwin--and why? One of the author's most baffling puzzles.