This is going off of very vague memory which may or may not be influenced by dreams. Walt went missing, and the others were all talking to him or something. The others said they were scared or something. Michael was like OHSHI I'M going to find my son!! Waltttt! Walllllt!!! Ben said if you leave on this raft thing, I will give you your son. (Or something) They left on certain bearings. Or apparently they left.

Now we see that Michael works for Ben, and Walt looks a lot older. My friend Eek thinks Ben knows how to control time skips depending on the bearings of the island, and he set Walt and Michael back three years, hence Michael possibly 'infiltrating' and Walt looking a hell of a lot older.