With a terminally ill wife, Glasgow mechanic Court Callany is desperate for money. When an acquaintance from work asks him to help him rob a wealthy antiques collector’s home, he reluctantly agrees. However, the robbery goes wrong, and when Court tries to sell his stolen artifacts at a local pawnshop, he unwittingly enters into the underworld of international relic hunting.
Prominent historian Dr. Nina Gould attends a primary school history week upon invitation, when a boy brings a suspicious relic to show-and-tell. Intrigued by it, Nina sends photographs of the ancient artifact to explorer David Purdue for examination. But what neither Nina, nor Purdue, knows is that the relic is reputed to be the sheath of the legendary sword of King Arthur - Excalibur.
As they investigate the origin of the scabbard with their colleague, investigative journalist Sam Cleave, they realize that they are embroiled in a dangerous network of traitorous people who would stop at nothing to hunt down the mythical sword. To exacerbate things, Nina is abducted and held hostage by a relentless war veteran.
While her time runs out, Sam and Purdue have to find Excalibur and trade it for their friend, or else Nina will die. Now, the two men are faced with a conundrum.
Will they be able to locate a sword that only exists in fiction and fable?
Or does Excalibur actually exist?