Bantam 101 (1947)

Synopsis:

When a detective falls in love with a beautiful dame who is supposed to be poisoning people - it's not good! And when he discovers that the man she is going to marry isn't doing anything to help save her beautiful neck - it's worse! But Inspector Elliot had an ace in the hole, that even her hot-headed fiancé didn't expect. When the going got too rough, he called in irascible Dr. Gideon Fell, the man who never fails to crack a joke at the wrong time or to get his man at the right time.

John Dickson Carr has concocted another humdinger in this sizzling puzzler, The Problem of the Green Capsule.