Blizzard of the Blue Moon

This installment in the Magic Tree House Merlin Missions series follows siblings Jack and Annie, who travel through time using a magic tree house belonging to Morgan le Fay, a magical librarian from the legendary realm of Camelot. The magician Merlin sends them on missions to prove they can use magic wisely, aided by two young sorcerers named Teddy and Kathleen. Having completed three missions to Venice, Baghdad, and Paris, Jack and Annie now await their next assignment.

On a gray November day in Frog Creek, Annie tells Jack the tree house has returned. Inside, they find a parchment scroll from Merlin with a poem outlining their mission: The last unicorn is hidden under a spell. Four centuries and four decades after the spell was cast, at the end of November before a blue moon (a rare second full moon in a single month), the unicorn will wake if someone calls his name, "Divine Flower of Rome," and coaxes him to stand, breaking his chain and the spell. A young girl must love the unicorn and show him the way home, or he will remain trapped on public display and all magic will fade from him. Annie declares she will be that girl. The research book Morgan has left, New York City Guide Book, 1938, puzzles Jack, since a unicorn is a fantasy creature and 1938 New York is a real place. Jack reviews their three remaining magic rhymes, none of which seems useful, then wishes to travel to New York, and the tree house transports them.

They land in Central Park during a snowstorm. From the tree house, Jack spots two figures on a hill, one in a dark cape and the other in a tan raincoat. He and Annie descend into the park but quickly become disoriented in the blinding snow. Jack catches a closer glimpse of the figures and speculates they might be Teddy and Kathleen, who secretly helped on their previous missions. When Jack realizes Annie is no longer beside him, he reads the rhyme "Find a Treasure You Must Never Lose," reasoning she is the most valuable thing in the world. Annie immediately reappears.

They find Belvedere Castle, where Bill Perkins from the U.S. Weather Bureau warns that two storm systems will merge after dark into a monster blizzard. He confirms tonight's full moon is the second of the month, a blue moon. When Jack asks about unusual animals on public display, Mr. Perkins suggests the Bronx Zoo and directs them to the subway. Outside Central Park, Jack and Annie encounter the hardships of the Great Depression, the severe economic downturn of the 1930s: People huddle in doorways, men line up for free soup, and newsboys wrap their feet in newspapers for warmth. They board the number 2 train, where Jack spots the caped-and-raincoated figures in a rear car. A girl in a purple shawl offers to tell them when to exit for the zoo but directs them to the wrong station.

A taxi driver offers to take them to the zoo, but the cab skids to a halt in deep snow. Jack and Annie trudge on until they reach the Cloisters, a branch of the Metropolitan Museum of Art devoted to medieval art. Inside, they find seven large tapestries depicting the Hunt of the Unicorn, woven in the Netherlands at the end of the 1400s. The final tapestry shows the unicorn alive, wearing a blue and gold collar and chained to a tree in a garden of flowers. Jack does the math: 1938 minus 440 equals 1498, matching the tapestries' creation date. All the clues align. Annie calls out "Divine Flower," and Jack tries "Divine Flower of Rome," but nothing happens.

Jack spots two people crossing the cloister garden. He and Annie hide to surprise them, expecting Teddy and Kathleen. Instead, they overhear Grinda and Balor, pale-faced teenage apprentices of a figure known as the Dark Wizard. Grinda reveals she and Balor followed Jack and Annie to find the unicorn. She raises her arms and calls the unicorn "Dianthus." Wind rushes in, the tapestry's flowers sway, and the woven unicorn moves his head. Grinda coaxes him to stand so Balor can capture him with a thick black rope and transport him to the Dark Wizard's castle. Annie shouts at the unicorn not to go to Grinda. A flash of light erupts, and the unicorn leaps out of the tapestry onto the museum floor as a glowing, milk-white creature with a spiraled horn.

Balor grabs the unicorn's collar and tries to loop the rope around his neck. Jack charges at Balor, who shoves him into the snow. Annie yells for Jack to use a rhyme, and he reads "Pull a Cloud from the Sky." Thick fog fills the cloister, blinding everyone. Jack and Annie find Dianthus in the fog and escape into the main hall. Outside, the unicorn kneels so they can mount him, then leaps over a snowdrift and runs into the storm before Balor and Grinda can catch them.

Dianthus gallops through the city, his spiraled horn piercing the blizzard. Wherever the horn shines, winds calm and snow softens. Snowbound taxis start moving, lights come on in cafés, and people break into smiles. Church bells ring. The unicorn leaps the wall into Central Park, where the clouds part to reveal sunset light. Annie shouts to the astonished Mr. Perkins at Belvedere Castle that the monster storm is not coming. Dianthus stops at the tree holding the magic tree house.

Balor and Grinda emerge from behind the tree, having taken the subway to arrive ahead of them. They seize the unicorn's collar and prepare the rope. Annie recites the "Turn into Ducks" rhyme from memory, and the two apprentices transform into mallard ducks that fly away with a passing flock.

The yellow taxi reappears, and the driver and the girl in the purple shawl reveal themselves as Teddy and Kathleen. They explain they guided Jack and Annie all along: Kathleen directed them off the subway early because Teddy was waiting, disguised as the taxi driver, to take them toward the Cloisters. Teddy explains that "Divine Flower" translates to "dianthus" in Latin, the language of Rome, the key to Merlin's clue. Morgan le Fay and Merlin then step from the taxi. Merlin explains the unicorn was stolen from Camelot long ago and hidden in the tapestries by magic weavers to keep him safe. He declares Jack and Annie have proven they can use magic wisely and presents them with the Wand of Dianthus, a spiraled wand shaped like the unicorn's horn and containing some of his magic. Morgan adds that the wand can only be used after they have tried their hardest and only for another's good.

Teddy and Kathleen ride Dianthus home to Camelot, vanishing in a flash of silver. Jack and Annie climb into the tree house as the blue moon rises over Central Park and wish themselves home to Frog Creek. Annie mentions they have one rhyme left, but Jack reveals he already used it to find her in the park, because he considered her the most valuable treasure in the world. Touched, Annie thanks him, and they head home through the snow for their dad's hot chocolate.