The sheriff orders the musketeers to give chase. Billy pulls off his hat to reveal himself and shouts for them to stop, buying his friends a few more seconds. The sheriff recognizes him as Sir William of Goat and orders his arrest. As the musketeers close in, Walter mutters that the Sunday school picnic has stopped being fun.

Walter’s remark about the Sunday school picnic triggers an idea. Billy declares that arresting him would require the musketeers to arrest themselves, since doing so on a Sunday violates the church’s rules. The confused musketeers hesitate. Walter whispers that it’s actually Tuesday, but Billy whispers back that in this world it’s not. The sheriff, unable to counter the argument, concedes that it’s indeed Sunday and announces that all arrests are postponed until noon the following day, at which point Billy, Robin Hood, Hercules, and Tom Sawyer will be marched to the gallows. The sheriff limps away.

Walter erupts with admiration for Billy’s quick thinking. Billy then lays out the next steps: They need to find a book that will help them rescue their friends and, afterward, enlist Tom Sawyer’s help to locate the treasure. Walter wants to see Pollyanna and eat some pie before they leave the island, and Billy agrees.

That afternoon, back at Dr. Libris’s cabin, Billy and Walter go through their host’s special bookcase hunting for the right book. Walter proposes Alice’s Adventures in Wonderland, but Billy worries it could introduce the violent Queen of Hearts and make things worse. Walter also reveals he checked his own copy of Robin Hood at home and confirmed that the events on the island hadn’t altered the original text: The sheriff there does not limp, and there are no French deputies. The book itself is unchanged, meaning only the island is unusual.

Walter suggests they simply leave the island’s characters to their fate and find the treasure with someone else. Billy refuses, insisting they can’t abandon them. Walter concedes, and the boys agree to split any treasure evenly between the two of them, with a possible share for Tom Sawyer.

Around six, they settle on Jules Verne’s Journey to the Center of the Earth as their solution. Its underground monsters should frighten off the sheriff without introducing too many new complications. Walter heads home, and Billy reads alone in the study until his eyes grow heavy. He wakes up at 2 am, puts the book away, goes to bed, and hopes the monsters will stay underground.

In Lab Note #322, Dr. Xiang Libris reports that the Theta Project has produced its first tangible, potentially marketable result. Walter brought Pollyanna into existence by reading Pollyanna under the dome. He then obtained a slice of huckleberry pie from her at the picnic and carried it off the island. Though there are no cameras inside Walter’s cottage, Dr. Libris observed a vivid red stain on Walter’s shirt that afternoon. It was left by huckleberries that had originated as a fictional pie, confirming that an imaginary object had become physically real.

The next morning, Billy arrives at the Hodgepodge Lodge to find Walter’s younger sister, Alyssa, sitting on the back steps wearing a life jacket. Alyssa insists on coming to the island and threatens to scream so loudly that their mothers and all the neighbors will ban anyone from going to the island if they refuse. Billy and Walter relent and take her along.

On the island, Pollyanna immediately charms Alyssa and proposes a picnic in the open field, giving Billy a plan: They can leave the two girls in a safe place while he and Walter hike to Tom Sawyer’s cave to unleash the Jules Verne monster. Billy reads aloud from Tom Sawyer to identify the cave, an A-shaped entrance on a molar-shaped mountain, and the boys set off, aware it’s nearly noon.

They climb a steep, narrow trail with a sheer drop on one side. When they spot the cave entrance, they hear boots on the path behind them and dash inside to hide. The cave is dark, cold, and empty of Robin Hood, Hercules, and Tom Sawyer. The boys squeeze into a side chamber just as the Sheriff of Nottingham and the four musketeers appear at the cave’s mouth.

The sheriff and musketeers enter the cave with lanterns, moving deeper inside. Walter urges Billy to summon the monster from the Jules Verne book, but silently rereading the passage does nothing. Billy begins reading aloud as fast as he can, describing the shark-crocodile. The sheriff hears his voice and identifies him.

From deep within the cave, the voices of Robin Hood, Maid Marian, and Tom Sawyer ring out, warning everyone to run. The three burst past Billy and Walter’s hiding spot and out into the open. A thunderous roar shakes the cavern walls, and Hercules shouts a warning about the approaching “sharkodile.” Billy is frozen with fear. Hercules charges up from the darkness, scoops both boys under his arms, and carries them out of the cave.

Outside the cave, the sheriff demands that everyone be arrested, but the sharkodile, a school-bus-sized creature with a crocodile’s body and a shark’s head, thrusts itself out of the cave entrance. The sheriff declares he is retreating to London and flees down the hill. D’Artagnan lunges at the beast with his sword, but the sharkodile snaps the blade in half. The monster wrenches itself free of the cave entrance and turns on D’Artagnan.

Hercules shoves D’Artagnan clear and plunges into the creature’s open jaws, using his body as a wedge to hold its mouth open. He asks Robin Hood to target a specific blackened tooth. Robin’s arrow strikes it, and the tooth pops free. The sharkodile instantly stops thrashing. Hercules steps out of its mouth, and the creature begins licking him. It had a painful cavity, and the tooth simply needed to be removed.

The now-docile sharkodile retreats into the cave. Athos steps forward on behalf of the musketeers to declare their debt to Hercules for saving D’Artagnan and swears they’ll never again raise their swords against any of Robin’s group. Everyone shouts the musketeers’ motto together: “All for one […] And one for all!” (146).

Walter nudges Billy about the treasure. They show Tom the slip of paper promising great treasure on the island. Tom confirms his belief that pirates buried treasure there, noting it’s typically hidden under rotting trees or in haunted houses. Billy and Walter promise to return the next day with shovels. They collect Alyssa from her picnic with Pollyanna and head home.

At the dock, they encounter Farkas getting onto his Jet Ski with a rolled-up booklet in his pocket. When Farkas demands to know what’s happening on the island, Billy deflects by claiming they’re only bird-watching. Farkas guns his Jet Ski toward the island anyway. Walter anxiously asks whether Billy locked the gate, and Billy confirms he did.

The following morning, Billy wakes up feeling optimistic and brainstorms books with haunted houses. At breakfast, however, his mother looks distressed. She tells him his father is driving up that afternoon to discuss something “extremely important.” Billy loses his appetite. His mother says she’ll signal him with a boat horn if she needs him before his father’s expected arrival at three. Shortly afterward, Walter arrives looking worried and holding a thin library book. He tells Billy they have a serious problem.

In Lab Note #323, Dr. Xiang Libris reports that developments are advancing so quickly he feels compelled to leave his remote observation post and relocate to his secure lab on the island. He’s confident that the research will soon make everyone involved wealthy.

Billy and Walter row toward the island, arguing. Walter insists they must deal with the giant from Jack and the Beanstalk, which Alyssa brought in her backpack and Pollyanna read aloud. Billy blames Walter for not checking his sister’s bag, and Walter blames Pollyanna. From his dock, Farkas taunts them and mentions he encountered someone dressed as Jack on the island the day before, confirming the character is already visible to outsiders.

On the island, they find a massive boot print in the clearing. Pollyanna appears, cheerfully remarks that the giant is “surprisingly different,” and reveals the Sheriff of Nottingham never fled to London. He’s remained on the island posting new wanted posters. She hands them one, which now lists Robin Hood, Hercules, Maid Marian, Tom Sawyer, and Sir William of Goat, whom the sheriff still blames for his injury.

A boy in tattered red clothing wanders out of the forest. Walter recognizes him as Jack from Jack and the Beanstalk. Billy instructs Jack to chop down his beanstalk, but Jack refuses until he has secured the goose that lays the golden eggs. The boys follow Jack to his cottage, where a beanstalk as wide as an oak tree grows in the yard.

Before they can act, the ground shakes. A 50-foot giant, who’s so tall his head nearly scrapes the wire-mesh dome covering the island, tears the roof off Jack’s cottage searching for him. He accuses Jack of stealing his singing harp. Jack mentions his mother had been sorting black pepper the previous day, and the giant unleashes a colossal sneeze that sends the boys tumbling into the open. The giant spots them and advances. The three run through the forest and reach a locked, electrified chain-link fence surrounding a mysterious cinder-block building topped with a satellite dish. Jack scrambles over the fence via an overhanging tree branch just as the giant’s footsteps shake the ground again.

Billy bluffs the giant, telling him that Jack has already climbed back up the beanstalk to steal the goose that lays golden eggs. The ruse works, and the giant lumbers away. Billy plans to wait briefly and then run back to chop down the beanstalk.

Before they can move, a six-foot gecko in a silver space suit carrying a ray gun steps out of the trees. Billy identifies it as the Space Lizard, likely summoned from one of Farkas’s comic books when the bully visited the island. The giant climbs the beanstalk in the distance, the massive vine having punched a hole through the dome overhead. The Space Lizard spots the commotion and moves off toward Jack’s cottage.

The boat horn blares from across the lake. Billy tells Walter he must leave to be with his parents and promises they’ll return later.

Back at the cabin, Billy notices his father has brought barbecue supplies and groceries. He overhears his parents on the porch and puts on a cheerful face to greet his father, who embraces him and produces a brand-new iPhone as an early birthday present. His birthday is in September, and the premature gift makes Billy suspect his parents aren’t reuniting. He sidesteps the looming conversation by announcing he needs to charge the phone and retreats to his room, where he lies face-down on the bed, wishing he could return to the island, where stories tend to end well.

Billy spends the afternoon trying to avoid his parents. He visits Walter at the Hodgepodge Lodge, and the boys hang out in Walter’s bedroom. Walter apologizes for the giant situation, and Billy promises they’ll fix everything the next day.

At the cookout, Billy stalls by eating three burgers. His mother quietly pulls him aside and tells him his father has sold a screenplay and intends to move to Los Angeles permanently. Billy and his mother will remain in New York. Rather than respond, Billy jumps up to collect sticks for roasting marshmallows.

Near the tree line, he runs into Alyssa, who tells him Walter lied to their mother that the two boys were camping on the island overnight together. Walter left in the family canoe about an hour ago, taking her library copy of Jack and the Beanstalk with him. Billy realizes Walter is now alone on the island after dark, surrounded by a 50-foot giant and an acid-spitting Space Lizard.

Billy decides the fastest way to get to Walter is to have his parents’ conversation immediately. He tells his father he is ready to talk, and his mother steps away as his father settles them into two lawn chairs and begins to explain the separation. Billy mentally tunes it all out. He learns his father will sleep in the living room that night before departing for Los Angeles. His father says he’s glad they talked, but Billy feels worse than before and asks to be excused.

As night falls, Billy thinks about Walter, who is alone on an island full of dangerous characters.