Grampa Jonas Flick was an antagonist in Doctor Sleep. At the time of events in the novel, he was their oldest member by appearance and Turning. At one point he is stated to have been around in the time of Henry VII, and at another, since the people of Europe worshipped trees. He is also stated to be a military history buff, and he tells rubes that he is a war veteran, though every twenty years he changes which war he was a veteran of. He has claimed to be a veteran of the Spanish-American Civil War, World War I and at the time of his death claimed to be a veteran of World War II. Had he lived, he would have eventually claimed to be a veteran of the Vietnam War. Depending on how long it has been since he took steam, his hair may either be white or gray, and he may or may not need to be pushed in a wheelchair. He is also stated to sometimes be unable to remember his own name. He is also one of the only three members of the True Knot who can track children with the shining, the other two being Barry the Chink and Rose the Hat. He was the first to die from measles and to activate Rose's urgency in capturing Abra Stone in order to hopefully inoculate them from the disease.
Grampa Flick first appears with Rose the Hat and Barry the Chink tracking a possible new recruit, Andrea Steiner. They follow her into a movie theater to watch Raiders of the Lost Ark and witness her hypnotize a man into going to sleep before capturing her and bringing her to their group. After she agrees to become one of them, he leads the ritual to initiate her, which she survives.
Grampa Flick later takes steam with the True Knot following Tommy the Truck's death, which makes him feel well enough to dance. He later helps track Bradley Trevor, and consumes him with the others.
After this, he starts to come down with something, and the other members of the True Knot realize something is happening to him. Rose eventually orders that he be examined, not wanting to lose him. By this time, however, it is too late, and he is already dying from the measles. The women in the True Knot watch over him for a while, but eventually he dies and disappears. This causes Rose to decide to pursue Abra immediately.