A film projectionist longs to be a detective, and puts his meagre skills to work when he is framed by a rival for stealing his girlfriend's father's pocketwatch.
In 17th century France, young D'Artagnan wants to join the King's Musketeers, but instead befriends three legendary musketeers—Athos, Porthos, and Aramis—and together, they become embroiled in the political intrigue surrounding King Louis XIII and his adversaries, particularly the powerful Cardinal Richelieu.