The Adventure of the Lost Boy — Barbara Hambly

A Sherlock Holmes fantasy novelette of 9,000 words - narrated by Mrs. Watson - As a child, Mary Watson had an imaginary friend: Peter Pan. When Peter is blamed for the disappearance of a nobleman's young heir, Mrs. Watson, now all grown up, discovers that her husband's friend Sherlock Holmes also knows Peter, and has agreed to help Peter Pan locate the Lost Boy in the Neverlands, and find who carried him off, before the King of Dreams closes the gates of the Neverlands against all children, forever.