Later

Stephen King uses the motif of illness, both physical and mental, to represent the consequences of giving in to one’s inner darkness. Uncle Harry gave in to temptation and lust when he took advantage of his younger sister Tia, Jamie’s mother— though the novel doesn’t specify the exact circumstances of Jamie’s conception. Professor Burkett’s daughter is also revealed to have a mental health condition; she is left catatonic after having murdered her child and trying to die by suicide. Finally, as Liz sinks deeper into corruption, she loses touch with reality, unable to distinguish lies from truth. Liz becomes so lost in rationalization that she believes she’ll be able to atone for premediated crimes.

Jamie assumes his ability to speak to the dead is associated with Uncle Harry’s (his biological father’s) early onset Alzheimer’s. Uncle Harry is able to see Therriault standing behind Jamie at the nursing home, and Therriault tells Jamie that he inherited a “condition” from his relative. As this “condition” is unspecified, it’s possible that Uncle Harry’s Alzheimer’s disease and the ability to see ghosts are linked.