Once you enter the Returner Hideout, go forward to the guard and speak with him to be allowed inside. He’ll bring you to a door; go on through. Here, you’ll find a Save Point nearby. Use it if you wish, then speak with the man, Banon, at the southern end of the room. He’ll introduce himself to you and you’ll watch a cutscene before regaining control of Terra, alone.
Time for some treasure hunting. Begin in the room you awoke in and open the chest for a Phoenix Down . Exit the room and head north to find an Air Knife , a Knight’s Code , and a Phoenix Down . Walk around to the east side of the chest trio and go east into the hidden passage; at the end, you’ll find a White Cape . Now, exit the room. On the way, examine the pot and bucket next to each other to find an Antidote and an Ether .
Outside of that room, go to the southeastern corner of the area and north a bit. You’ll notice some armor with a pot nearby. Examine the latter to find a Green Cherry . Go north to find Banon’s room and open the chest within for a Hi-Potion . That should cover the majority of the treasures.
Go around the hideout and speak to Locke, Edgar, and Sabin. Then leave the cavern portion of the hideout to find Banon. Speak with him and you’ll be able to make a choice. The following scenes still have the same end result, but follow different paths to get there, so to speak. If you answer "Yes" to his question on the first, second, or third try, you’ll receive the Gauntlet . This allows you to hold one weapon in two hands to double your Attack power, more or less, though you lose the ability to use a Shield. However, it is also a bit more common than the other choice…
Anywho, there will be a meeting. Locke heads to South Figaro, while Sabin, Edgar, Banon, and Terra will head to Narshe via the Lethe River.
If you answer "No" three consecutive times to Banon, Terra will walk into the hideout and wonder how anyone could put hope in her. Suddenly, Banon and a wounded Returner walk in. Locke, Sabin, and Edgar also come in. Locke will leave for South Figaro; Sabin, Edgar, Terra, and Banon will head to Narshe via the Lethe River.
During the conversation, it is interrupted by a Returner giving you the Genji Glove . Truly a good reason to do so, for it allows you equip two weapons at once, despite losing the ability to use a Shield. So, either way, you’ll end up with Locke leaving the party (and his equipment), sticking Terra, Banon, Sabin, and Edgar on the Lethe River to Narshe. We’ll end up controlling the latter party for the moment. When you regain control, go south and outside. Then board the raft.