Beware the Curves  (English, Paperback, Gardner Erle Stanley)

John Dittmar Ansel walked into the Cool-Lam office and asked them to trace a man named Karl, who, six years before, gave him an idea for a story. Donald Lam - always the suspicious one - immediately smelled a rat. And his nose had not betrayed him: investigation proved that Mr Ansel wasn't a writer at all; and Karl had died by a bullet. Bertha Cool and Donald Lam decided that this was a case worth pursuing, and before long they found they were not the only ones with a vested interest in the six-year-old mystery.