The chimes of Big Ben are heard and the Curtain-Up Music begins. As the music swells to its conclusion, Holmes and Watson appear. "Come Watson! The game's afoot!" announces Holmes -- as they exit and the show begins.
On busy Baker Street, people are mulling about, musing that The Game's Afoot as they observe the many curious people they see there. A group of young street urchins enter -- they are the "Baker Street Irregulars" -- Sherlock Holmes' eyes and ears on the streets of London who help in solving some of Holmes' most baffling cases. Their leader is Wiggins, a colorful character who aspires to be a master detective one day. A young lad named Georgie wanders in and tells Wiggins he's an orphan who has come to London to makes his way in the world. Wiggins explains that he and his friends work for a consulting detective named Sherlock Holmes who pays them well for clues. After they test Georgie's powers of deduction, Wiggins -- who thinks he's a natural -- says "yer in!"
The scene transitions to Holmes' and Watson's rooms at 221-B Baker Street and we hear Holmes playing a sonata on his violin, which he claims helps him concentrate and solve some of his most perplexing cases. Holmes asks Watson to come to the window, observe a curious fellow walking down the street, and use his powers of deduction to tell what he can surmise about the man. Although Watson tries his best to use The Art of Deduction, Holmes points out that his conclusions are all wrong and explains to Watson how he was mistaken. Just then, Mrs. Hudson shows the curious man in, and he announces he is the Queen's bodyguard, though Holmes had already deduced this before he had even arrived. He advises Holmes he has come from Queen Victoria herself to engage him in finding a missing crown jewel, the Star of India, stolen from the Tower of London. Watson finds the Bodyguard most irritable and demanding. Yet -- for the sake of the Empire -- Holmes takes the case, saying he will engage the services of the Baker Street Irregulars to help look for clues.
Later, the Irregulars meet, and Wiggins tells the boys that Holmes has hired them to help on his latest case. Just then, Lestrade walks by and suspiciously asks the boys if they know anything about the jewel thefts that are happening around town. They cleverly evade his questions, and although he tells them that Scotland Yard pays well for information, Wiggins says that Sherlock Holmes pays better! When Lestrade leaves, Wiggins tells the lads that The Case is Most Irregular and that they need to get on it right away. He begins handing out assignments, sending them out to various parts of London, and seizing an opportunity to instruct newcomer, Georgie, in the diner methods of deduction, Wiggins takes Georgie with him. As they run off, Georgie literally runs into a man who peers at him interestingly. It is Professor Moriarty. Moriarty notices that Georgie is wearing a fancy ring on a chain around his neck and offers to buy it. Georgie tells him it's not for sale when Tilly -- Moriarty's henchwoman enters and purposefully bumps into Georgie as he hurriedly runs off.
Tilly meets with Moriarty and hands him a handful of jewels. Moriarty scolds her doing business in public and tells her that he is in total control of the situation and that all is going according to plan. When Tilly tells him Holmes is on the case, Moriarty tells her that He's No Match for Me. Afterward, Moriarty tells Tilly not to worry about Lestrade, but keep an eye on Holmes and the Irregulars -- they might get in the way.
Back at Baker Street, Mrs. Hudson eavesdrops on Holmes and Watson as they discuss the new case and offers her services as a consulting detective which Holmes ignores, simply asking her for tea biscuits. She comments to Holmes and Watson about some of their former cases and says that she could have easily solves the Curious Clues if they'd only listened to her. Later -- using a map of the City of London, Holmes plots out the location of the jewel thefts and tells Watson that there is seemingly a pattern to the location of the heists and that he believes it could only be Moriarty who is behind them and he must have a greater evil scheme in mind.
In a London alleyway, Tilly meets up with Moriarty who gives her a myriad of jobs to accomplish. As he leaves, Tilly is upset that the Professor piles on the work and never gives her credit for all she is doing. She muses that she is so much smarter than the Professor knows and she smugly exclaims Don't Mess with Tilly.
The ensemble muses once again that The Game's Afoot as Holmes and Watson arrive at one of the jewelry stores where a jewel heist has taken place the night before. Inspector Lestrade and his men are there and tell Holmes they have thoroughly gone over the scene and have found no clues. Magnifying glass in hand, Holmes meticulously inspects every nook and cranny -- The Arts of Deduction Instrumental 2 -- and finds several clues Lestrade has overlooked. Holmes deduces that two robbers were actually involved in the theft -- a tall man who smokes a certain variety of tobacco and a small woman who came in through the window. Wiggins and Georgie enter giving Holmes an update on their findings. Holmes greets Georgie, glad to have him on the team. Holmes gives them each further assignments and tells Watson he has an errand for him at the Royal Library. As all exit, Tilly emerges, having eavesdropped on Holmes' observations. She shyly proclaims once again Don't Mess with Tilly. (Reprise).
At 221-B Baker Street, Holmes is playing is Lovely Violin, contemplating the set of clues around the London jewelry heists. He knows the clues are leading him to "his old friend" Moriarty, but with "every dance of the bow" he resolves that he will indeed solve the case.
On a London street, Wiggins continues to school the Irregulars in Holmes' philosophy of deduction. Wiggins challenges Georgie that there's something about him he "just can't figure out." The Irregulars agree and observe that Georgie speaks in a more refined manner, holds his tea cap "with his little pinky up" and he's far too "polite." Georgie is flustered, but is assured of their friendship. He is relieved that They Likes Me Just Fine.
At Convent Garden, people are milling about as Tilly and Moriarty enter. An old man with a fruit cart asks Moriarty if he would like to buy an apple. Moriarty dismisses him, though Tilly says she'll "'ave one a' them" -- though she is shocked at the price of two pennies. She is clearly impressed with herself and pleased to report to Moriarty everything that she has recently observed about Holmes and Lestrade. However, she doesn't like "our friend" at all, "prancing about and smoking cigars" while she does all the work. Moriarty assures her that the "friend" serves a "necessary purpose." Moriarty is confident that the "royal package" will soon be delivered to them, but by none other than "Lestrade himself." As they begin to exit, Georgie and Wiggins are not far behind, following them -- but not before Wiggins steals an apple from the old man's cart. Wiggins and Georgie still agree The Case Is Most Irregular (Reprise) -- but are determined to help solve it. Doctor Watson enters, is very befuddled as the old man removes his disguise, revealing to Watson that in actuality he is Sherlock Holmes -- then hurries along to further pursue the case.
While Holmes and Watson are out, Mrs. Hudson is back at 221-B Baker Street. It is Mrs. Hudson's Lament that she is always kept in the dark on all of Mr. Holmes' cases. One by one, visitors come and go -- from Inspector Lestrade to the Baker Street Irregulars, to the Queen's Bodyguard. She grudgingly informs all of them, "Mr. Holmes is out as as usual I have no idea where he is or when he'll be back." Finally Dr. Watson arrives, looking for Holmes -- hoping he picked up the books Watson had retrieved from the Royal Library. She confirms to Dr. Watson her ongoing frustrations that she has no idea where Holmes is. Watson assures her that "Mr. Holmes often leaves me in the dark as well." Mrs. Hudson is still certain that she would "make a fair detective."
In a London Alley, Wiggins brags to the Irregulars that he helps himself to a "little dessert" while practicing his "slight of hand" and stole an apple from an old man's fruit cart. He promises to go back tomorrow and give the old man a tuppence -- and asks his friends if any of them "got one?" Georgie reaches into his pocket for the tuppence and is shocked to pull out instead a string of pearls and jewelry. The Irregulars accuse him of stealing the jewels and just as he is defending himself, Lestrade enters, and seeing him with the jewels, proclaims him and all the Irregulars just "a bunch of petty thieves." Wiggins confirms Lestrade is right about Georgie -- he is a thief because he stole the jewels from him. Protecting Georgie and all the Irregulars, Wiggins takes the fall and is hauled off the Scotland Yard by Lestrade. Together the Irregulars conclude that Tilly must have planted the jewels on Georgie when she deliberately bumped into him -- creating a distraction for Lestrade and Scotland Yard. The Irregulars rush to find Holmes and seek his help to free Wiggins.
Back at 221-B Baker Street, Holmes advises Watson that he had "an interesting visit" with his "friends at the London Times" -- Watson's research from the Royal Library has proved to be "most essential" to the case -- and the Irregulars recently provided him with "some important news." Holmes is off to meet with Lestrade and reminds Watson he will have Lestrade meet him later at the "arranged place" -- "the center of the hexagon." Holmes declares the "British crown is at stake" and advises Watson to being his "army service revolver."
And The Fog Rolls In, as the ensemble enters, commenting that there is danger in the air -- so beware! The chimes of Big Ben are heard once again as the scene shifts to the Tower of London where Moriarty is waiting for Holmes, who appears. The two meet at last.
Moriarty boasts that Holmes' methods are so predictable and he would come. Holmes announces that he is well aware of Moriarty's true objective -- the theft of a "single jewel" that Moriarty claims is so priceless that Queen Victoria will give him anything he wants for its return -- in fact, a "Queen's ransom." Moriarty takes the Star of India from his pocket -- tosses it to Holmes so he may see if one last time -- and in that moment, as Holmes lunges for the jewel, Moriarty grabs a fencing sword from the crown jewel case -- thrusting it at Holmes -- who also grabs a sword and the two begin The Duel. As the fencing match intensifies, Moriarty claims he is the superior swordsman, but as they lock swords, Holmes reveals, that "on the contrary" he "studied with Captain Hutton" a famous expert in obsolete fencing. Holmes out-maneuvers Moriarty, disarming him.
Suddenly Wiggins and the Baker Street Irregulars enter. Their entrance distracts the two men, as Moriarty grabs his sword -- then Georgie, and holds him captive. Holmes commands Moriarty to release Georgie, but he refuses and begins to leave. Wanting to rescue their friends, the Irregulars charge and overtake Moriarty, causing him to drop his sword and allowing Georgie to go free. Moriarty escapes, warning Holmes, "We'll meet again!" The Irregulars exclaim that Moriarty is getting away, but Holmes assures them that Doctor Watson and the entire London Police force have been waiting outside the Tower of London for quite some time. Just then, Wiggins spies the Star of India, picking it up and presenting it to Holmes who declares it a "priceless piece of British history." Lestrade enters with Moriarty in handcuffs. Moriarty is still confident that next time he'll be "the one who wins." A London Bobby and Tilly exit, Watson is pleased the case is sewn up and promises that his readers are sure to enjoy his account of the story in his upcoming chronicles. Holmes advises him to "not write your story yet" and to "come along for a but of unfinished business at 221-B Baker Street."
The Ensemble once again reminds all that The Game's Afoot (Reprise) -- with clues that have yet to be revealed. Watson, the Irregulars and Lestrade all assemble at 221-B Baker Street wondering why Holmes has summoned them there. Suddenly all our astounded when Queen Victoria and her Bodyguard enter, where, she too is puzzled as to why Holmes has called her there. Holmes presents the Star of India to the Queen who expresses her gratitude to him and that of the British Empire. All feel the case has been solves, but Holmes announces, "The real jewel is still missing." He explains that Moriarty created a series of jewelry robberies to distract Holmes and Scotland Yard -- then steal the Star of India to further distract everyone as he stole "a jewel even more valuable." With the Queen still baffled, Holmes further explains that Moriarty wasn't counting on the loyalty of friendship, as Wiggins took the fall for Georgie. Holmes reveals that the jewels had indeed been planted on Georgie so that he would be taken to jail where a "boy of little interest" could be easily taken away by the "not-so-trustworthy Captain of the Royal Guard!"
The Queen's Bodyguard is outraged as Holmes announces, "Here's your crown jewel thief, Lestrade, the accomplice of one Professor Moriarty." The Bodyguard vehemently denies in being involved in any schemes of Moriarty's -- or being an accomplice to Tilly. He pulls out his sword form his cane, warning all the "Stay back!" Just then, Queen Victoria takes her cane and whacks him over the head, bringing him down. Lestrade handcuffs him and leads him off. Watson asks, "So the jewel thief is caught? What else is missing?"
Holmes explains that while disguised as a fruit seller in Convent Garden, he had overheard Moriarty and Tilly's plan, noticed Wiggins steal his apple, and most importantly had noticed the ring that was hanging around Georgie's neck. As Holmes confirms, it was a crest he had seen before, a perfect hexagon that was the center of Moriarty's true plan. Thanks to Watson's "expect research" at the Royal Library, Holmes discovered the signet ring was indeed the rest of the house of Hanover. Holmes further reveals that his own research at the London times provided him with information about a missing "jewel, so to speak" from the crown. Holmes removes Georgie's cap, and her long hair tumbles out, revealing that he is actually a she, the real missing jewel of the House of Hanover, Queen Victoria's niece, Georgiana Andrea Elisabeth Catherine -- third Duchess of York -- foruth Duchess of Kent. The Queen is overwhelmed with joy to find her long missing niece and the Irregulars are shocked, as Wiggins exclaims, "Blimey! You're a girl!" Georgie explains that she was disguised as a boy in order to find work in London. She adds that she had no idea she was ever a member of the Royal Family as her parents, who lives in the country, had dies when she was very young and she had been taken in by friends. Queen Victoria and her niece embrace and she thanks Sherlock Holmes for returning the "missing jewel" to her and solving the intriguing case. Delighted to be of service to the crown, Holmes calls down to Mrs. Hudson to bring up "cookies for the boys." As the Queen had been secretly squired into Holmes' room unbeknownst to Mrs. Hudson, she enters, and shocked to see the Queen, faints into the arms of Dr. Watson. Holmes assures the Queen that when Mrs. Hudson recover, "you'll find her biscuits most delicious."
With the case resolved, the ensemble enters, as all muse that The Game's Afoot (Finale) still -- with many mysteries yet to be solves as Holmes is summoned back to Scotland Yard "for a case of the utmost importance!" The curtain falls.