Thirteen-year-old Meg Murry finds herself grappling with the challenges of both school and home life, particularly since the mysterious disappearance of her father, Alex. Alex, a respected scientist conducting research in astrophysics, vanished under enigmatic circumstances, and both Meg and her mother, Kate, suspect that he may have cracked the code of humanity's existence, leading to his teleportation to another realm.
One fateful night, Meg's curious younger brother, Charles Wallace, invites a peculiar stranger dressed in a large white gown, Mrs. Whatsit, into their family home. Mrs. Whatsit captivates them with intriguing news about the Tesseract—a form of space travel that Alex had been researching—and departs just as mysteriously as she arrived. The following day, meandering through her daily routine, Meg encounters classmate Calvin O'Keefe, who soon becomes embroiled in their extraordinary adventure when they visit the enigmatic Mrs. Who, another eccentric woman known for her cryptic quotes, who appears to be familiar with Charles Wallace.
In a surprising turn of events, Mrs. Whatsit reappears, accompanied by Mrs. Who and Mrs. Which, the oldest of the trio who looms over them as a gigantic figure. Together, they unveil their true identities as astral travelers, revealing that they ventured to Earth in response to a distress call emanating from the universe, presumed to be from Meg's father, stranded in an unfathomable expanse. Their mission: to navigate through a Tesseract to the distant planet of Uriel.
Once on Uriel, the transformation of Mrs. Whatsit into a stunning green being allows the children to ascend into the planet's atmosphere, yet they soon encounter a menacing figure known as The IT. Described by Mrs. Which as representing the darker facets of humanity—greed, anger, pride, and low self-esteem—The IT has ensnared Meg's father. Additionally, Mrs. Which introduces them to Happy Medium, a seer residing on another planet. Through this encounter, Meg learns of her father’s captivity on the sinister planet of Camazotz, underscoring The IT's malevolent plan to dominate the universe.
As their journey unfolds, Meg comes to understand that even seemingly popular peers, such as Calvin and the school bully Veronica Kiley, harbor deep insecurities. The triumvirate of Mrs. Whatsit, Mrs. Who, and Mrs. Which suggests a return to Earth for regrouping. However, as Meg obstinately resists, their haphazard navigation of the Tesseract inadvertently transports them directly to Camazotz.
Upon their arrival, the trio discovers they cannot remain due to the malevolence saturating Camazotz, and they grant Meg three invaluable gifts: the glasses of Mrs. Who, the revelation of her own shortcomings, and the unwavering encouragement to maintain unity among the three of them. Their perilous trek through the ominous landscape of Camazotz leads them to an eerily populated beach, where they confront Red, the IT’s intimidating bodyguard. Red attempts to lure the children with food and false reassurances about Alex's wellbeing, yet they quickly realize something is amiss when Charles Wallace succumbs to the hypnotic cadence of Red's recitation of multiplication tables.
As Meg and Calvin chase after Charles Wallace's trance-induced presence, they become ensnared in a desolate room. Utilizing Mrs. Who's glasses, Meg discovers a hidden staircase that leads to the chamber where her father remains imprisoned. After a thrilling rescue, the insidious influence of The IT redirects Charles Wallace's allegiance, forcing an encounter with its formidable power. While Calvin and Meg begin to fall under The IT's sway, Alex activates another Tesser to make their escape, but Meg's refusal to leave her brother behind demonstrates her fierce love and determination.
In a decisive moment of realization, Meg uncovers that The IT thrives on deception and hatred. With an unwavering surge of love for Charles Wallace, she conquers her own imperfections and liberates him from the clutches of The IT, ultimately shattering its dominion over Camazotz. The trio of extraordinary women returns to inform Meg that her journey is only just beginning, as she embarks on her own quest through the Tesseract.
Upon returning, Meg expresses her heartfelt gratitude to the women for their guidance and for rescuing her father. As they part ways, Meg finds herself in an unexpected truce with Veronica, who has transformed into a friend. The film culminates in a heartwarming reunion for the Murry family, while Calvin prepares to confront his own challenges at home, signaling the beginning of new chapters in their lives.
