Matt Bird writes all sorts of nonsense, but he dedicates a large chunk of his time to writing game walkthroughs.
Sabin's crew is on their way to Narshe, and Locke is hauling a former Imperial general along as he treads through the sands of Figaro. That leaves Terra, Edgar and Banon still to arrive, blasting along the rapids of the Lethe River.
The trip to Narshe picks up right where you left off, only your party is down one member. With Edgar's Auto Crossbow, Terra's magic and Banon's Pray, this shouldn't be a problem; blast your way through the enemies blocking your path to Narshe. Soon enough you'll debark by the lake next to Narshe. Figaro Castle hasn't yet resurfaced and South Figaro Cave is blocked by an Imperial soldier, so your list of destinations is thin. Enter Narshe.
The guards recognize Terra immediately and prevent you from entering the town through the front entrance. Fortunately, there's a secret way in - the way Locke used to get out last time. Go west of the entrance and check the rock face to access the mines.
Head through the mines until you reach a second indoor section. This spot is small, but it's worth noting that the enemies in here are a fair bit stronger than the ones in the first sections of the mine. If you want to power-level your little party anywhere in Narshe before the end of the scenario, this is the place to do it. (Even if you don't plan on power levelling, this is a good place to earn a lot of money quickly. You'll need lots of gil to fully outfit your party when you next gain access to shops.)
The next room is this scenario's sole puzzle. In order to pass through here, you must follow the exact same path as the dot of light that zips through the rock formations. Fail to do this and you'll get caught in a trap. You can escape the trap by tapping A when the yellow light along the edge of the cage reaches your character; otherwise, you'll get into a fight and get thrown back to the beginning. Success sounds like a given, but for completion's sake you'll want to get caught and fight two or three times until you face the three foes unique to this room alone: Darksides, Specters, and Eukaryotes. After you complete this puzzle, you'll lose the chance to fight these enemies ever again.
Through the north exit of this room is the section of mine where Terra fell while being chased at the beginning of the game. You can take this path east and go straight to the old man's house, but you'll miss a fun little part. Take the southern door along the eastern path and you'll wind up in the area where you protected Terra using the Moogles. Go through the northern door here.
You'll find the Moogles themselves! The fuzzy white creatures are shacked up in great numbers here, and they'll happily welcome you in a language you can't hope to understand. (In case you were wondering, yes, that is Mog standing still.) The chest in the rear of the Moogle's cave contains a Runeblade, not a terrible weapon, but if you wait until a revisit in the second half of the game, you'll find a Ribbon instead. The Ribbon is by far the superior piece of equipment.
Go through the exit south of the chest and you'll be back in the mine Terra explored early in the game. Go south to find the way out of the mine and to the rear of the old man's house (his name is Arvis, by the way). This will bring the scenario to a close.