Plot
A young man and woman are chased by a group of hooded men intent on killing them and taking a device that they carry. As they are surrounded, the man Paul reassures his companion that Gwendolyn will be safe, that Grace will protect her. Just as the men are about to kill them, Paul and the young woman activate the device and disappear.
The film fastforwards sixteen years later, to the day before Gwendolyn "Gwen" Shepherd's sixteenth birthday. She belongs to an aristocratic London family who do not believe in associating with "commoners". They look down on Gwen because she, her mother Grace, and her brother Nick are the only "normal" family members. The family gathers for a party in honor of Gwen's cousin Charlotte, who is one day older than her. They hold a special regard for Charlotte as she possesses a secret genetic mutation, inherited by only one female per generation, that gives her the ability to travel back in time. At the party, Charlotte taunts Gwen about being unable to get a date for the school ball. Gwen is attracted to Gideon de Villiers, but he only has eyes for Charlotte. When Charlotte suddenly becomes ill, Gideon rushes her to a mysterious secret society, the Order of Count Saint Germain; he apparently is a carrier of the same gene. Believing Charlotte to be the "Ruby", the long-prophesied last time traveler, the Order inducts her.
Shortly afterwards, Gwen also becomes ill and begins seeing ghosts. She goes out to get some fresh air and stumbles into the nineteenth century. The only person she tells about this time jump is her best friend Leslie, who quickly recognizes that Gwen must be the one who inherited the time travel gene instead of Charlotte. Gwen makes several more uncontrolled jumps in time and learns about a conflict between her family and the Order. Gwen finally tells her mother about her time traveling. Grace recognizes that Gwen is the Ruby and brings her to the Order for help controlling her ability. Gwen's aunt, Charlotte's mother, does not believe her and accuses her of attempting to be the center of attention. The Order's guards fear a conspiracy, since decades ago Grace helped the previous time travelers, Lucy and Paul, escape. Gideon, also known as Diamond, does not want to work with Gwen because of his closeness to Charlotte—they have been training together for years for a mysterious "mission"—who in turn is upset about being replaced by Gwen.
Gwen is eventually confirmed as the so-called "Ruby", the last of twelve time travelers, but has doubts about the Order, the mission, and the Chronograph, a device the Order can use to control the time traveling of the twelve travelers. Lucy previously helped steal the Chronograph because she was afraid of a terrible power it held. Gwen still is unsure what exactly is going on, but at the Order, she is given an unlimited spending account, and Gideon is warned to keep an eye on Gwendolyn, and is also warned against any love affairs between the two time traveling families. Gwen overhears him say that she is definitely not his type.
Due to the theft of the previous chronograph by Gwen's cousin Lucy, blood samples have to be collected from all of the formerly living carriers to finish a second device. Gideon is unable to collect blood from Lady Tilney, Gwen's great-great-grandmother, as she knows Gwendolyn's name and will only cooperate with Gwendolyn. When Gideon and Gwen visit Lady Tilney in 1912, Lucy and Paul suddenly appear, warning Gwendolyn of the dangers of finishing the Chronograph and of the Count's plans to sacrifice her life to achieve his goals. Gideon overpowers Paul and the butler and runs away with Gwen. Back in the 21st century, Gwen takes Gideon out to a "common" restaurant for some Indian food, which is a new experience for him.
Back at headquarters, only Gwendolyn believes in Lucy and Paul's sincerity, while the Guardians are convinced of a plot by the Florentine Alliance that has been fighting the Count of Saint Germain for centuries. Falk de Villiers, grandmaster of the lodge, wants to control Gwen and is worried about her curiosity, but Gideon starts having some twinges of doubt. Charlotte taunts Gwen with her close relationship with Gideon. Gwen breaks the Order's vows of secrecy and shares about her experiences with her friend Leslie. Charlotte recruits a teacher at the school, who is a secret member of the Order, to stop them. Gideon picks Gwen up at the school with a limo, which impresses her classmates.
Gwen goes to meet with the Count of Saint Germain in 1782. He is able to read minds but is not impressed with Gwen and will not answer her questions. The Count wonders what the Ruby's special magic is. Gwen does not know. When she talks about the future to his companions, he chokes her Darth Vader style and warns her not to break his rules. Gwen questions Gideon about his blind obedience to the Order even though he knows little about their goals.
On the way back, their carriage is attacked in Hyde Park. During the fight, Gwen saves Gideon's life, and he is forced to reevaluate how he sees her. Gwen wants to run away from the Order but Gideon says they can't because the Order "owns" them. Ultimately he decides to search with her for answers. He kisses her as thanks for saving his life, which Charlotte observes from a window.
At night, they sneak into the Order's archives to find an ancient prophecy about themselves, but the secret documents were transferred to a bank years ago. Using a note from Gwen's grandfather, they convince Mr. George to help them travel to 1942 to find the documents. In 1942, they read the prophecy about how Gwen's death as the Ruby (a.k.a. "the Raven"), bleeding out in the snow, will bring the circle of the twelve to completion. The last part of the prophecy is torn off and missing. Security guards break in, and in trying to escape, Gwen falls many stories to the ground from the top of the observatory tower. After being unconscious for some time in the snow-covered courtyard, Gwen wakes up in a pool of her own blood. The Count then comes in spirit form to confront her. Meanwhile, Gideon is thrown into the dungeon. The ghost of a little boy whom Gwen has been seeing throughout the movie appears and helps keep Gwen discover that Lucy's talisman she has been carrying is actually a key to help her get into the building and stay alive.
Again in the present, Gwen is found unconscious from hypothermia. Falk de Villiers quotes the prophecy of her icy death and tries to prevent any efforts to save her life. But Gideon defies this instruction and carries Gwen in the doctor's room. When she recovers, he promises her to always take care of her.
Gwendolyn goes to the big school ball wearing her cousin Lucy's dress and being accompanied by Gideon. She discovers from a family photo that the little boy she has been seeing is her grandfather's dead younger brother, and she concludes that her ability to see ghosts could be the special "magic of the raven." At the ball Gideon and Gwen share a kiss while a ghost dances nearby. The film concludes with Paul and Lucy escaping again from another group of men who are chasing them.
