The problem of Thor bridge

It was a wild morning, and the last remaining leaves were being whirled from the solitary plane tree which graced the yard behind the house. Holmes was in a good mood, with that somewhat sinister cheerfulness characteristic of his lighter moments. After a month of trivialities and stagnation, he had a case. First published in two parts, The Strand Magazine and Hearst-s International Magazine, February and March 1922.