Locke throws Desmond down an electromagnetic well

Locke and Desmond's journey comes to an end at an old well, but not the one near the Orchid Station where Ben and Locke turned the frozen donkey wheel. Desmond looks down the well trying to guess how deep it is and Locke throws a torch down that hits the bottom.

Locke tells Desmond that this well is so old that the people who dug it did it completely by hand. He says that these people dug it to understand why their compass needles spun uncontrollably at this particular spot, but they never found what they were looking for.

Locke continues, saying that he showed Desmond this well because Charles Widmore is only interested in power, not answers and he plans to use Desmond to find what he's looking for. He adds that this is not the only well. These wells all seem to be built over pockets of electromagnetism, so is this what Zoe was asking Jin about? Do they need Desmond to survive another Swan Station or Incident-style blast?

Moving on, Locke asks Desmond why he's not afraid to be out here with him considering no one knows they're there. Desmond says "What's the point in being afraid?" Locke's expression turns sinister and he throws Desmond down the well.

So there's still the big mystery as to why Desmond is so zen now. We still don't know what he knows in either timeline.