Two-part episodes aren't usually strengths of "Mission: Impossible." The tension of the caper can sometimes be lost when stretched to fill two episodes. At first, "The Slave" looks like it's going to fall prey to the padding that marred "Old Man Out" in Season 1. But as we get into the episode, particularly towards the end of Season 1, we see one of the team's most daring missions taking shape.
Everybody has a part to play...Barney and Willy even get to don disguises. There's a lot of set-up with gadgets and tricks in this episode that won't really pay off until the next episode, but the neatest trick (the frozen bats) is used to good effect in the climax.
What makes this an interesting episode is that, in order for the plan to succeed the team must abduct and potentially harm an innocent (the prince's wife). I liked how the quandry was not lost on the team, as Jim tells Barney to make it as easy on her as he can. Any instances on this show when we got to see the team struggling with their assignments were great to watch; it gave some subtle layers of character to the players who otherwise just acted their roles in the mission each week.