In the Country of the Musketeers, Mickey, Donald, and Goofy are fending off a Dream Eater, but with little success. Sora comes in to save them, but Mickey doesn't recognize him. Sora is confused at first, but then he remembers that the Sleeping Worlds are in the past. Still, he doesn't understand, because the last time he saw Mickey's past, it was in Timeless River, which went on to become Disney Castle. Even though this Mickey is from the past, he still knows about the Keyblade and the existence of other worlds. He tells Sora that he went to that world because there was something wrong there. More Dream Eaters appear, but Sora manages to destroy them.
Sora offers to accompany the Musketeers on their journey, but they have to initiate him as a Musketeer first. They hold their swords (and Keyblade) in the air and shout "All for one, and one for all!" In a flashback, we see the captain of the Musketeers, Peg-Leg Pete, officially making them Musketeers and giving them a mission to protect Princess Minnie. Back in the present, the Musketeers are escorting Minnie on a carriage when a large Dream Eater called the Tyranto Rex attacks. Sora manages to destroy it, but three criminals called the Beagle Boys show up and kidnap Minnie. The Musketeers make their way to the Beagle Boys' tower and confront the trio at the top. They fight, and the Musketeers manage to defeat them.
The Musketeers return from their mission, which takes them the rest of the day. Donald tells them that he learned that Pete was actually the mastermind the whole time and that he plans to kidnap Minnie. Sora is surprised to learn that Pete is the captain. He summons some Dream Eaters and manages to knock both Sora and Mickey out. Once Sora regains consciousness, Donald and Goofy tell him that Pete took Mickey to a place called Mont Saint-Michel where he plans to drown Mickey. Donald and Goofy are reluctant to go save him, but after some encouragement from Sora they agree to help.
Sora, Donald, and Goofy make it to Mont Saint-Michel just in time to save Mickey from drowning. He begins to despair, but Sora and friends manage to cheer him up. They make their way to the Opera House, where they see the Beagle Boys handling a chest with Minnie inside. They reach the stage, where Pete tries to spring a trap on them. He has a large crate fall on top of Mickey and friends, but it suddenly vanishes before hitting them. Sora realizes that Riku was the one who saved them, and he has the Musketeers send Minnie away while he fights Pete and the Beagle Boys. After defeating them and saving Minnie, she gives them the title of "Royal Musketeers." Later, Sora finds the Sleeping Keyhole in the courtyard. He unlocks it and continues his search for the Spellican.
Meanwhile, back at the Mysterious Tower, Lea is explaining things to Yen Sid. The Master tells Mickey and friends that the reason he chose such an unusual test for the Mark of Mastery was because Sora and Riku needed to obtain a special power, which they needed to unlock the Sleeping Keyholes to get. Unfortunately, Yen Sid is no longer able to locate Sora and Riku, which he chalks up to Xehanort's intervention; since Lea was restored to his human self, Xehanort must have been as well. Yen Sid warns Lea that if he tries to help them, it will not be easy, but Lea is still willing to help. With that, they begin to formulate a plan which they hope will outsmart Xehanort...
