It was in the cold bleak autumn following the spectacular Dragon murder case that Philo Vance was confronted with what was probably the subtlest and most diabolical criminal problem of his career. Unlike his other cases, this mystery was one of poisoning. But it was not an ordinary poisoning case: it involved far too clever a technique, and was thought out to far too many decimal points, to be ranked with even such famous crimes as the Cordelia Botkin,...