Shortly after finding out she is about to be proposed to, a 19-year-old Alice flees an engagement party. In doing so, she discovers a rabbit named Nivins McTwisp wearing a blue waistcoat. Intrigued, Alice decides to follow it, even as far as stumbling down his rabbit hole. After her fall, Alice lands into Underland, a post-apocalyptic fantasy land, where various animals have apparently been expecting someone called "Alice". While Nivins claims that she is Alice, the other animals are under the impression that she is "The wrong Alice".
She then meets up with Tarrant Hightopp, who is happy to see her, but Alice doesn't remember him. When the Red Queen's minions come to him looking for her, Tarrant gives Alice a potion that shrinks her, then hides her in a teapot and pretends that he's never seen her, after Stayne leaves. Alice gives Tarrant a piece of her clothes, and Tarrant then makes a strapless dress for her and gives it to her. Tarrant takes Alice on a journey to Marmoreal, and explains the Red Queen's reign of terror over Underland on the way. Soon, the Red Queen's minions pick up Alice's scent, and start chasing them. With no other options, and the enemy approaching, Tarrant puts Alice atop his hat and flings it across a river to the opposite side (saving her from the Red Knights), but then draws attention to himself, and gets captured in the process. He is then taken away as Alice watches on. Alice then hides inside Tarrant's hat, and spends the night there. Later, she is found by Bayard, who wants to take her to the White Queen, but Alice insists upon helping the Hatter, so they go to the Red Queen's Castle.
She enters the castle, then she is found by Nivins McTwisp. He gives her a piece of cake to make her grow, but she outgrows the clothes she was wearing. The Red Queen notices an abnormally large girl near one of her hedges, and investigates. At this point, Alice discovers that she's naked. Nivins McTwisp, who had been a page to The Red Queen since he was captured by the Knave of Hearts, tries to come up with an excuse of what this girl is. While hesitating, he says "um," which the Red Queen takes this literally. Alice, while posing by the name of Um from Umbridge, explains to the queen that she towers over everyone in Umbridge, and that because of that, she's a laughing stock. The Red Queen, who is now under the impression that Um is a beautiful but misunderstood and shy giantess, gives her a warm welcome, stating that "Anybody with a head that large is welcome in my court."