Lost Season 3 episode 3 - Further Instructions

Synopsis: "The fates of Locke, Eko and Desmond are revealed after the implosion of the hatch, while Hurley returns to the beach camp to tell the tale of what happened when he, Jack, Kate and Sawyer encountered "The Others." Meanwhile, Claire is shocked to find Nikki and Paulo [new cast members Kiele Sanchez and Rodrigo Santoro] in Jack's tent."

Well, great episode, just like the last season.

Locke is back in great style.

Stop here! Spoilers!

After the hatch explosion (or implosion?) Locke can’t talk anymore.

Then, he creates a hallucinogen and has a vision, where Boone appears to be his guide and tell him he'll be able to talk when he has something worth saying. At the end of the vision, Boone tells Locke that he has to clean up his own mess.

Locke and Charlie go to search for Eko, who was dragged into a cave by a polar bear. Locke rescues Eko, and takes him back to camp.

Desmond shows up in front of Hurley naked, and apparently already knows a speech Locke is going to give.

The episode ends with Locke telling Claire, Paulo (Rodrigo Santoro) and Nikki that he is going to find their friends.

Locke’s flashback: he worked and lived on a rural commune, and seems he was (presumably) part of a drug organization or something like that.

Theories:

One of the skeletons in the polar bear cave was wearing a shirt with the logo from the Pearl, which implies that members of the Dharma Initiative became prey to their own experiments.

It seems that Desmond can now tell the future as he knew Locke's speech before it happened. Perhaps he had gotten this power because he was closest to the fail-safe when he activated it in "Live Together, Die Alone".

Source: Lostpedia