The Musketeers - Season 3 Episode 10 We Are the Garrison

Following Treville's funeral the musketeers survive an attempt by Grimaud to kill them when their garrison is torched, leaving many casualties, and gunpowder and weapons stolen. To lure the musketeers into a trap Grimaud takes hostages including Sylvie but the four comrades stage a rescue, and the queen and Dauphin are restored to the palace with Milady as the royal spy master, her first task being to take care of Gaston. However, the mortally wounded Grimaud escapes and the musketeers must stop him from blowing up the city with the stolen gunpowder.