Elementary, it is not. In fact, the Adventure of the Bizarre Copyright may be the most complicated Sherlock Holmes case to date, a baffling mystery involving an army of copyright lawyers, a disputed literary legacy, the psychological profiling of the great fictional detective and Mickey Mouse. The estate of Sir Arthur Conan Doyle is suing Netflix over the film Enola Holmes, based on the young adult novels by Nancy Springer, in which Millie Bobby Brown plays Holmes’s independent-minded younger sister, solving cases of her own.

In Britain, all of Conan Doyle’s works have been in the public domain since 2000, 70 years after his death, but in the US, where the suit has been filed, the handful of stories written between 1923 and 1927 are still under copyright. The Holmes portrayed in these later works, the estate claims, is markedly different from his earlier incarnation: warmer, cuddlier and more human, in contrast to the cocaine-fueled, unfeeling super-brain of the early Sherlock. The Sherlock in Enola Holmes, played by Henry Cavill, known for portraying Superman, is touchy-feely and emotionally aware, say Conan Doyle’s heirs, and therefore the film infringes copyright.

A study in copyright: Conan Doyle at work in his garden.

For amateur sleuths, the case hinges on whether the later Holmes really does show substantially different character traits in the later stories, and if so, why.

Brain Teaser

In The Greek Interpreter (1893) Watson describes Holmes as “a brain without a heart”. Aloof and unemotional, he has no time for feelings, friendship or women. “I am a brain, Watson,” he says in a later story. “The rest of me is a mere appendix.” He treats his closest companion with little evident warmth. Holmes does not even congratulate Watson when he announces he is marrying Mary Morstan. He prefers Watson quiet and biddable: “You have the grand gift of silence, Watson.”

The First World War changed not only Conan Doyle, his heirs argue, but also his most famous character. The author lost both his eldest son and his brother to the conflict. He became increasingly fascinated by spiritualism. The complaint alleges that in the stories written after 1923, a very different detective emerged: “Holmes became warmer. He became capable of friendship. He could express emotion. He began to respect women.” He even displays affection for dogs, of the non-Baskerville variety.

Seeing and observing: Conan Doyle and his family.

The most famous evidence used to suggest that Holmes has developed empathy comes in the 1924 story The Three Garridebs, in which Watson is shot in the leg.

Holmes is frantic with concern: “You’re not hurt Watson? For God’s sake, say that you are not hurt?”

“It was worth a wound,” observes Watson. “It was worth many wounds, to know the depth of loyalty and love which lay behind that cold mask … for the one and only time I caught a glimpse of a great heart as well as a great brain.”

So that, as far as the Conan Doyle estate is concerned, is case closed: anyone who depicts Holmes as a compassionate, caring, dog-loving detective is in breach and should cough up.

For amateur sleuths, the case hinges on whether the later Holmes really does show substantially different character traits in the later stories.

But as in all Holmes stories, the truth is elusive. Conan Doyle was inconsistent in his portrait of Holmes. The detective displayed emotion long before 1923. In The Naval Treaty (1893) he goes all wobbly over a rose: “Its smell and colour are an embellishment of life.” In A Scandal in Bohemia (1891) he is clearly smitten by Irene Adler, an American opera singer. Watson insists “He never spoke of the softer passions, save with a gibe and a sneer,” yet “to Sherlock Holmes she is always the woman … In his eyes she eclipses and predominates the whole of her sex.”

As for Watson, while Holmes may treat him dismissively in the early works, he has great affection for his sidekick. The detachment is a “mask”. It is only after he has been shot that Watson, who is not very bright, realizes this, in a “moment of revelation”.

Warm and cuddly or brainy and cocaine-fueled? The answer is not so elementary …

Holmes, like most literary characters, is evolving, complex and sometimes contradictory. Chopping him up into phases and characteristics for the purposes of copyright is a bizarre way to approach literature. Every character in a written series, from Bertie Wooster to James Bond, is slightly different at different times, yet finally a single imagined being. Holmes is infinitely adaptable, and every age crafts a Sherlock in its own image. Over the years he has been cartooned, lampooned and psychoanalyzed, depicted as a child, a homosexual, an anti-Nazi hero and a lunatic; he has been translated to the stage, television, radio and over 100 films, played variously by Basil Rathbone, Peter Cushing, Benedict Cumberbatch, Robert Downey Jr and Ian McKellen. If Cavill plays Holmes as “emotionally connected”, that has less to do with violating copyright than reflecting modern male behavior.

The real reason for the Enola Holmes lawsuit lies in the 1998 US Copyright Term Extension Act, which prolonged copyright from 75 years to 95 years after publication. This is also known as the “Mickey Mouse Protection Act”, since it has kept Steamboat Willie, the first Disney film featuring Mickey, under copyright.

Millie Bobby Brown on the set of Enola Holmes, the Netflix show that started it all.

The great Conan Doyle copyright saga will end in 2023, when the last story slips into the public domain. But the copyright on Steamboat Willie is due to expire the following year. Will the anthropomorphic mouse with the yellow shoes be made available for adaptation by anyone? Will Disney argue that only the simple character portrayed in the first cartoon is in the public domain, while the later, more sophisticated Mickey remains under copyright? Or will the law step in to protect The Mouse once again?

The game’s afoot. And it is quite a three-pipe problem.

Ben Macintyre is the author of several books, most recently The Spy and the Traitor: The Greatest Espionage Story of the Cold War