3. The Lion's Mane
The Lion's Mane comes from the much maligned latter part of the Doyle canon. Found in The Casebook of Sherlock Holmes the least acclaimed of all Holmes collections, the story takes place after the detective's retirement in Sussex and is relatively unusual in that it is one of only two stories narrated by Holmes himself. What is more unusual about The Lion's Mane is the baddie in short, a jellyfish did it. Holmes witnesses the death of a man whose last words are "lion's mane" and sets about solving the seaside mystery. He ultimately deduces the involvement of the guilty jellyfish and then beats it to death with a rock. Doyle was well and truly tired of writing Holmes by the 1920s, and nowhere does it show more than in this absurd outing. While Holmes' meticulous, unromantic narrative style makes it something of an interesting read in contrast to the usual spritely adventurousness of the Watson-narrated stories, this is one of the weakest stories in the canon and would just play as a complete joke if adapted for Sherlock. Plus, Watson isn't in it, and could anyone forgive an entire episode bereft of Martin Freeman?