The hot-headed young D'Artagnan (Logan Lerman) joins forces with three veteran Musketeers to prevent the villainous Cardinal Richelieu (Christoph Waltz) from seizing the French throne and engulfing Europe in war in this fast-paced, action-filled reboot of Alexandre Dumas' classic 17th-century adventure. When famed Musketeers Athos (Matthew Macfayden), Aramis (Luke Evans), and Porthos (Ray Stevenson) steal highly coveted airship designs from a high-security vault, the sweet taste of success is short-lived. Their beautiful partner in crime, Milady (Milla Jovovich), drugs the trio and sells the designs to a higher bidder, the ultra-cool Englishman, Buckingham (Orlando Bloom). It's a major blow to the famed swordsmen. So when, three years later, the devil-may-care young D'Artagnan journeys to Paris to realize his dream of becoming a Musketeer, he finds them a shadow of their former selves, working menial jobs and seeking a cause worth serving.

The conniving Cardinal Richelieu hatches a deadly plot to overthrow the young King Louis (Freddie Fox). Employing the double agent Milady to do the dirty work, he frames the King's new bride, Queen Anne (Juno Temple) in an affair with Buckingham. If the King buys into the lie, war with England will follow, the Queen will die and the people of France will demand a stronger leader - Richelieu himself - to see them through the crisis. If the King doesn't buy into the lie, peace may yet stand a chance. But for peace to be ensured, the three Musketeers and their young apprentice must undertake their most dangerous mission ever - to retrieve a priceless diamond necklace from the impregnable Tower of London and return it to the Queen in time for an all-important ball.