Desmond is now eager to help in original timeline, Sayid kills two men & takes him

When Desmond wakes back up in the original timeline, alive and well, Seamus and Zoe are both shocked, but Charles Widmore doesn't seem surprised at all. A nurse/medic starts to check his condition, but he waves her off, saying he's fine and asking Widmore to help him up.

Widmore tells Desmond he was only unconscious for a few seconds. He then starts to apologize, for putting Desmond through the test, but Desmond stops him, saying it's okay because he understands now. Widmore seems confused, but Desmond seems very zen and asks, "When do we start?"

Zoe and two other men start to walk Desmond through the Hydra Station grounds. She asks him what happened to make him go from beating Widmore about 20 minutes ago to being Mr. Cooperative. He says a lot can happen in 20 minutes. She says that the machine fried his brain. Suddenly, Sayid appears and kills the two other men. He points a gun a Zoe, but tells her to run. Sayid tells Desmond that Widmore's team are dangerous and they need to go. Desmond, Mr. Cooperative, says "lead the way" and follows Sayid.

So what exactly does Desmond now know in this timeline that makes him so zen? Does he know exactly what he needs to do, or is he just going with the flow?