Autumn arrives as the nature-talent fairies prepare to bring the season to the mainland. In Pixie Hollow, Tinker Bell, Mae Whitman is busy with a new invention intended to help her friend Terence, [Jesse McCartney], when a summons arrives from Queen Clarion, [Anjelica Huston], Fairy Mary, [Jane Horrocks], and the Minister of Autumn, [John DiMaggio]. They unveil a mystical moonstone and explain that every eight years, during the Autumn revelry, a blue harvest moon appears. Its light passing through the moonstone creates a luminous blue pixie dust, which rejuvenates the pixie dust tree. Tinker Bell is charged with crafting a ceremonial scepter to hold the moonstone and mark the ceremony.
She asks Terence to be her assistant, but his overeager efforts begin to wear on her patience. When asked to fetch something sharp, Terence brings a compass, which irritates Tinker Bell because he doesn’t notice the arrow inside. A misstep with the compass crushes her newly completed scepter, and her anger explodes in a loud outburst at Terence. He leaves, and in the aftermath, the compass accidentally smashes the moonstone itself, setting off a cascade of trouble.
At the theater, Tinker Bell learns of a legendary magic mirror that once granted two of three wishes before disappearing. After a heated row with Terence over extra pixie dust, she decides to seize the mirror’s third and final wish to repair the moonstone, and sets off in a balloon to pursue it.
During the journey, Blaze, a green firefly, crashes into Tinker Bell’s balloon, and she reluctantly allows him to accompany her. As they press on, Tinker Bell believes she has found the stone arch that supposedly leads to the mirror. She leaves Blaze to scout, but the balloon’s anchor gives way and it sails off. A gale knocks them from the sky, and they must press onward on foot.
When they awaken, aided by friendly insects, they are guided to the real stone arch. They reach a sunken shipwreck where the mirror lies buried, and there they finally locate it. Blaze’s buzzing begins to grate on Tinker Bell, and in a moment of impulse she wishes for quiet, wasting the mirror’s third wish. Realizing that her temper has caused the mess, she breaks down, apologizing to Blaze and longing to repair things with Terence.
Meanwhile, Terence has followed her trail and, after discovering her lost balloon, catches up with Tinker Bell. The two gladly reconcile, and Blaze joins them as they escape the ship pursued by a pack of rats.
On the return journey, Tinker Bell reassembles the scepter: she fits the mirror’s gem into the scepter, combines it with pieces of the original scepter that Terence had brought, and includes the compass arrow. The balloon lands in the center of the revelry, and Tinker Bell unveils the scepter—now set with moonstone fragments and the mirror’s gem—which refracts the blue light of the moon into countless shards. A vast plume of blue pixie dust erupts, renewing the magic of the season. Overjoyed, Tinker Bell, Terence, and Blaze lead the procession to carry the blue pixie dust to the pixie dust tree, where the entire celebration is illuminated by the dazzling display.
