7. "How does 'Insomnia' figure in to all of this?" (added in 1.4)

        The story behind Insomnia is rather simple, Ralph Roberts can't sleep. Eventually he starts hallucinating, seeing auras around people and seeing little bald men wearing white smocks who go around with sharp implements cutting the auras of the dying so they can truly pass from this world ("to other worlds than these ".) There are three "doctors", two of whom go about their work in a solemn and professional manner. They visit people who are sick and in pain and do what they can to end suffering. The third doctor is more chaotic, he gets a perverse thrill out of what he does and serves chaos by causing people (and animals) to die in tragic accidents. The doctors explain to the heroes of the story that life is like a tower, human beings and other Short-Timers inhabit the first two floors of the tower and are oblivious to things above them. They can however, be raised up to a higher level of consciousness and brought to see other levels through sleep deprivation. Long-Timers, such as the LBDs (Little Bald Doctors) can go down to do their work among the Short-Timers, but are themselves prevented from interacting with the All-Timers who reside even higher in this metaphorical tower. The creatures residing at the highest levels use the beings below them as pawns in a gigantic and unfathomable contest between the Random (chaos) and the Purpose (order.)

        It is later revealed that in addition to the regular inhabitants of the tower there are also those called "the Great Ones", people who are destined to change the world in dramatic ways. One of these great ones is (at the time of "Insomnia") a little boy with a scar across his nose named Patrick Danville. One of the inhabitants of the Tower appeared to a man named Ed Deepneau and convinced him to try and blow up a civic center for the sole purpose of killing young Patrick. This "Crimson King" wants the boy dead because eighteen years in the future he will save the lives of two men, one of whom (according to the two "good" LBDs) must not die. These two men are presumably Roland and Eddie (Patrick has been having dreams about Roland reaching the tower and confronting a man he calls "the Red King".) The forces of the Purpose have enhanced the lives of the heroes of "Insomnia" so they can prevent the Crimson King and the forces of Random from killing the child and thereby remove the agent that saves the men who will confront the Crimson King at his tower.

        Spoiler for the Final Book in the Dark Tower series: Patrick is actually the one who takes out the Crimson King. He doesn't destroy him exactly, but rather reduces him to a pair of burning, impotent, eyes.

        As a side note: when Short-Timers operate on the higher levels of the tower they become intangible to the people and things in the "real" world. Time also passes much faster, many days can pass over the course of a conversation. This could easily explain how Roland and the Man in Black held a conversation over the course of at least a hundred years, Roland was unknowingly dragged up a level and held there while he had his visions. In the mean time the Man in Black returned down to the real level and either died or killed himself, either way when Roland returned to the real world enough time had passed to turn his companion into a skeleton.