Professor Edward Johnston (BILLY CONNOLLY) and his assistant, Andre Marek (GERARD BUTLER), are leading a group of students on an archaeological dig at the ruins of a 14th century French castle at the village of Castlegard.
Long ago, following the hanging of a French woman, Lady Claire (ANNA FRIEL), the French forces were so enraged that they stormed the heavily fortified English castle and defeated their enemy. While that historical legend enthralls Johnston, Marek and students such as Kate (FRANCES O'CONNOR), Stern (ETHAN EMBRY) and Francois (ROSSIF SUTHERLAND), it means little to the professor's adult son, Chris (PAUL WALKER).
That changes when the group discovers a previously unearthed chamber that's been untouched for more than 600 years. Yet, not only do they discover a bifocal lens that wasn't invented until hundreds of years later, but they also find an ancient document. To their amazement, it's a handwritten plea for help from their professor dated April 2, 1357. After carbon dating and handwriting analysis proves the document's authenticity, the students head to the New Mexico headquarters of ITC, their expedition's sponsor.
There, they learn that Robert Doniger (DAVID THEWLIS) and his team have figured out a way of transmitting objects and people from one part of the world to another. Such research generated the unexpected discovery of a wormhole straight to 14th century France. Needing people versed in the culture of the time, Doniger recruits the students to travel back to 1357 -- along with marine Frank Gordon (NEAL McDONOUGH) and his team -- to rescue the professor and find and deal with a renegade worker who's stayed behind in that time.
Although they can't believe these amazing developments, the students agree and travel back to the site of their dig, only 600 years earlier. There, they attempt to find Chris' dad, all while dealing with the pending massive battle between the English, led by Lord Oliver (MICHAEL SHEEN), and the French headed by Lady Claire and her brother, Arnaut (LAMBERT WILSON), as well as an unexpected development back in the 21st century that threatens to leave them stranded in the past.