In the first half of the two-part season finale of Merlin, the attacking army of Morgana and the Southron warlord Helios overtakes Camelot, leaving Merlin and the wounded Arthur with no choice but to flee the kingdom. However, the stubborn young king is unwilling to retreat, even when hopelessly outnumbered, forcing Merlin to cast a spell that reduces Arthur to a polite, obliging simpleton. Disguised as peasants, the two go into hiding from Morgana's soldiers, only to be captured by a pair of smugglers whose names will be familiar to fans of Arthurian lore: Tristan and Isolde.

In these two SPINOFF-exclusive clips from “The Sword in the Stone, Part 1,” we get a glimpse of the assault on Camelot, and see Arthur (played by Bradley James) and Merlin (Colin Morgan) in the hands of Tristan and Isolde (Ben Daniels and Miranda Raison), criminals with no love for Camelot's king.

Merlin airs tonight at 10 ET/PT on Syfy.