The Irregulars are fans of Sherlock Holmes, dedicated to the "great game," the careful study and interpretation of Arthur Conan Doyle's work, grounded in the assumption that Holmes was real and Doyle merely Dr. Watson's "literary agent." But no one expected Stout to announce his discovery that Watson was the Great Detective's wife.
Here is Stout quoting from the Canon, and then explicating:
The reader may set me down as a hopeless busybody, and when I confess how much this man stimulated my curiosity, and how often I endeavored to break through the reticence which he showed on all that concerned himself.You bet she did. She would. Poor Holmes! She doesn't even bother to employ one of the stock euphemisms such as, "I wanted to understand him better," or, "I wanted to share things with him." She proclaims it with brutal directness, "I endeavored to break through the reticence." I shuddered and for the first time in my life felt that Sherlock Holmes was not a god, but human--human by his suffering. Also, from that one page I regarded the question of the Watson person's sex as settled for good.
Not surprisingly, Stout's tongue-in-cheek theorizing did not achieve overwhelming support. But it was published in the Saturday Review, and has been in print more or less ever since.