Motive v. Opportunity — Agatha Christie

At a meeting of the Tuesday Night Club, attorney Mr. Petherick relates an incident involving the late Simon Clode, a wealthy client. Obsessed by his granddaughter's death, Clode turned to spiritualist Eurydice Spragg to contact her in the afterlife, and then decided to write a new will leaving Eurydice as the benefactor and excluding his family. To everyone's surprise, when the envelope containing the will is opened, the paper is blank. The Tuesday Night Club goes on the case…