The Fifth Heartby Dan SimmonsLittle, Brown, 2015The Fifth Heart, the latest novel in the mother of all winning streaks from Dan Simmons, opens with an irresistible hook: it's 1893, and Henry James, on the eve of his fiftieth birthday, has come at night to the dark recesses underneath the bridge of le Pont Neuf in Paris, in order to throw himself into the Seine and commit suicide. But under the bridge he encounters – and is saved by – another man, a Norwegian explorer named Jan Sigerson, who'd come to the spot with the same goal in mind. The two men get to talking – testily, in James's case, since he immediately recognizes what all addicts of mystery-fiction will already have spotted even in such a brief summary: Jan Sigerson is an impostor.It's one of the false identities Sherlock Holmes assumed while the world at large thought he was dead, killed in battle with Professor Moriarty at the Reichenbach Falls a few years before. In Arthur Conan Doyle's 1894 story “The Adventure of the Empty House,” Holmes, returned to London, surprises poor Doctor Watson with the fact that he's still alive – and that he'd wandered far and wide in a series of disguises, including that of the Norwegian explorer Jan Sigerson. James spots at once the fictional character underneath the guise of a fictional character, and when Sherlock Holmes browbeats him into accompanying him to America in order to investigate the 1885 death of Clover Adams, the wife of James's old friend Henry Adams, Simmons' latest romp of historical fiction is off at a gallop.“I am lost without my Boswell,” Holmes tells Watson at one point, but Henry James is the least willing sidekick imaginable. Not only is he certain that this “Sherlock Holmes” is a lunatic, but he's affronted by the highly personal nature of the case in question; he hadn't forgotten, Simmons tells us, “that Clover's death was so traumatic to Adams that his historian friend had never once mentioned the day or details of her death in the more than seen years since the event.” In the novel's supremely entertaining early segment, the literary aesthete James takes up Conan Doyle's Holmes canon and rips through it with a hurricane-like thoroughness that will set Holmes fans angrily sputtering. “Proofreading errors were rampant,” he sniffs, and the famous detective's deductive powers were “merely silly.” A case in point would be the popular story “The Adventure of the Red-Headed League,” in which poor hapless Jabez Wilson is given the task of copying out the Encyclopedia Britannica:

The author also has “Wilson” mentioning that he was moving into the “B's” in the encyclopedia at the time the Red-Headed League was dissolved and he lost his silly job. Holmes had noticed the recent 1889 Ninth Edition of the encyclopedia in a hallway bookcase, and Henry James rang for a manservant to fetch the first volume of the Britannica. After actually counting the words on an “average” page in the first section, James hobbled over to the room's small writing desk, retrieved some foolscap and a pencil, and figured that the character of “Jabez Wilson” had copied some 6,419,616 words in eight weeks' work … and that while copying for only four hours a day! With a little division on his foolscap, James averaged this to a rate of some 33,435 words per hour or a little over 557 words per minute. Extraordinary!Ridiculous! The author, whether Watson or Conan Doyle, literally had not done his arithmetic.

This is brutal stuff, naturally, and enormous fun, as is James's huffy deduction from the canon that Holmes is “no gentleman.” But as Simmons steadily unfolds his enormously complicated plot, drawing in all the famous characters in the Adams circle back in America, from John Hay to Mark Twain to Henry Cabot Lodge to Theodore Roosevelt, the real surprise of The Fifth Heart becomes apparent: the touching humanity of Simmons' fictional worldview infuses what would otherwise be an elaborate tongue-in-cheek pastiche with a rich sadness and resonance. Even while James is investigating the basic appeal of the Holmes & Watson stories, we can watch this most introverted of all 19^th century authors overlaying his own stubborn loneliness onto the reading experience:

The heart of The Adventures of Sherlock Holmes lay not in the clumsy “adventures” - which never struck James as that adventurous – but rather in the friendship between Holmes and Watson, their breakfasts together, the foggy days shared indoors by the crackling fire, and Mrs. Hudson coming and going with her food trays and messages from the world. Holmes and Watson lived in a Boy's Adventure universe that, like Peter Pan, and despite Watson's rather confused mentions of being married, neither of them ever grew up.

Arrested adolescents abound in The Fifth Heart, and the pure note of sorrow that is the death of Clover Adams shades the whole playful machinery of the novel a gravity that takes the whole thing a big step beyond the simple literary parlor game it also so wonderfully is. Like his earlier novels Drood and The Terror, Simmons here lavishes on his readers with a historical novel unlike anything they'll read all year. And does Sherlock Holmes end up being merely a fictional character? Well, the answer was always elementary.