The future of the English monarchy rests on the musketeers' shoulders after Louis orders them to recover the Queen of England's missing crown jewels. It's a daunting mission, made more complicated when they unmask the thief. Fighting every instinct, the Musketeers must place their faith in an old adversary to hunt down the diamonds. The ensuing mayhem tests each of their loyalties to the limit, and a surprise reunion results in heartbreak for Aramis. Meanwhile, Feron seizes an opportunity to avoid personal scandal.