A tense chase opens the film as a young man and a woman are pursued by hooded attackers who want a mysterious device they carry. Surrounded, the man reassures his partner that loved ones will be safe, that Grace will protect her, and with a final act, they activate the device and vanish into the past.
Sixteen years later, Gwendolyn Shepherd, Maria Ehrich, is introduced as a sixteen-year-old in an aristocratic London family that scorns anything “common.” The family gathers for a party in honor of Gwen’s cousin Charlotte Montrose, who is a day older and carries a secret genetic mutation that grants her the ability to travel back in time. Gwen is drawn to Gideon de Villiers, Jannis Niewöhner, but he fixates on Charlotte. The party reveals a sharp divide between Gwen’s normal life and the closed, secretive world her relatives inhabit. Charlotte, who has long been the center of attention, suddenly falls ill, and Gideon escorts her to a secret society known as the Order of Count Saint Germain; he appears to be a carrier of the same gene. Believing Charlotte to be the prophesied “Ruby,” the last time traveler, the Order inducts her.
Gwen herself soon falls ill and begins seeing ghosts, and her time jumps grow uncontrolled. She confides in her best friend Leslie, who quickly recognizes that Gwen must be the true inheritor of the time-travel gene rather than Charlotte. Gwen’s powers set off a chain of events that reveals a deep rift between her family and the Order. Grace Shepherd, Veronica Ferres, recognizes Gwen as the Ruby and leads her to the Order for help. Meanwhile, Gwen’s aunt—Charlotte’s mother—doubts Gwen’s story and suspects attention-seeking rather than truth. The Order’s guards fear a conspiracy, especially since decades earlier Grace helped the previous time travelers, Lucy and Paul, escape. Gideon—also known as Diamond—worries about his long history with Charlotte and the mission they have trained for, while Charlotte resents being replaced by Gwen in the group’s plans.
Gwen is eventually confirmed as the so-called Ruby, the final piece in a circle of twelve time travelers, but she remains wary of the Order, their mission, and the Chronograph, a device the Order could use to control their time traveling. Lucy Montrose, Josefine Preuß, had previously helped steal the Chronograph out of fear of its power. To complete a second device, the Order needs blood samples from all past carriers, but Lady Tilney, Gwen’s great-great-grandmother, will only cooperate with Gwen and no one else. The team travels to 1912 to seek her help, where Lucy and Paul suddenly appear to warn Gwen about dangers ahead. Gideon and Gwen barely escape with the help of Mr. George, Rüdiger Vogler, and return to the present, where Gwen treats Gideon to a taste of the world Gwen’s life has opened up—that of a place Gwen calls “common” by contrast.
Back at the Order’s headquarters, only Gwen believes Lucy and Paul’s sincerity, while the Guardians suspect a centuries‑old scheme between rival factions—the Florentine Alliance and the Count of Saint Germain. Falk de Villiers, Uwe Kockisch, the lodge’s grandmaster, worries about Gwen’s curiosity, and Gideon begins to doubt how blindly he’s followed the Order’s rules. Charlotte taunts Gwen about her growing closeness with Gideon, and Gwen dares to break the Order’s vows by sharing what she’s learned with her friend Leslie. In turn, Charlotte enlists a teacher who is secretly a member of the Order to foil Gwen’s progress. A sleek limousine upgrade impresses Gwen’s schoolmates when Gideon arrives to pick her up.
Gwen eventually travels to 1782 to meet the Count of Saint Germain, who can read minds but is unimpressed by Gwen’s claims. He probes her about the Ruby’s true power and warns her not to break the unwritten rules. Gwen questions Gideon about his unquestioning obedience to the Order and what they truly aim to achieve. On the way back, a carriage in Hyde Park is attacked. Gwen saves Gideon’s life, forcing him to rethink how he views Gwen and the Order’s control over them. She longs to walk away, but Gideon insists they cannot because the Order “owns” them. He finally chooses to stand with her and help uncover the truth, a decision Charlotte observes from a window with a mix of envy and resolve.
That night, Gwen and Gideon sneak into the Order’s archives to uncover an ancient prophecy about their bond, but the crucial documents have been moved to a bank. With a note from Gwen’s grandfather, they convince Mr. George to help them travel to 1942 to access the missing records. In 1942, they read a prophecy predicting Gwen’s icy death in the snow, which would complete the circle of twelve travelers. The final fragment of the prophecy is missing, and security guards chase the lovers as Gwen falls from a high observatory into a snowy courtyard. She wakes in a pool of her own blood, the Count appearing in spirit form to challenge her fate. Meanwhile, Gideon is imprisoned, and the ghost of a little boy Gwen has seen all along helps her realize that Lucy’s talisman is the key she needs to stay alive.
Back in the present, Gwen is found unconscious from hypothermia. Falk de Villiers quotes the prophecy to discourage any rescue attempts, but Gideon defies orders and carries Gwen to safety. As she recovers, he pledges to protect her no matter what. Gwen learns that the ghostly boy is her grandfather’s deceased brother, revealing that her ability to see spirits may be the legendary “magic of the raven.” At the big school ball, Gwen arrives in Lucy’s dress and is escorted by Gideon. A family photo confirms the boy’s identity, and Gwen realizes that this spectral presence is part of her unique gift. The moment is sealed with a kiss between Gwen and Gideon as a ghost dances nearby, and the film closes with Paul and Lucy escaping once more from their pursuers.
