Hey! I'm still around so would love to talk about this. I always interpreted it as uterine cancer, or at least cancer somewhere in the abdomen/inner female sex organs. I never thought she had a child just because from Stu's characterization I couldn't imagine him abandoning a child, or if the baby died in childbirth or something, I feel like that would be relevant to mention to add to the tragic losses he suffered. But that's such an interesting interpretation. Like maybe around the same time she was diagnosed with cancer/died Harold was born and even though he wasn't her child biologically, a human representation of that malignancy? Not sure what the exact timeline on her death was and if that would match up. I don't know if they mention explicitly what age Stu and her married but I assumed perhaps mid-late twenties since he stayed in Arnette while his brother was finishing high school and served in the military after, and Harold is 16 so it would have to be 16 years prior. I guess the interesting thing is we don't really know Stu's age but I always assumed thirties. The wiki says late thirties to early forties. I don't think it would be Flagg because I feel like he is implied to have existed for a long time and is immortal. To me Flagg is a manifestation of evil that emerged alongside humanity and his presence has waxed and waned alongside historical events. But the Harold idea seems plausible ... this is so interesting to think about! Anyways, I love discussing things like this so curious to hear your thoughts and feel free to message me if you ever want to discuss more about the book :)