Donna starts out a little bit evil this season, assuming the identity of Nurse Rita to bring Mr. Jingles into Camp Redwood. But we see a redemption arc when she survives the 1984 murders and helps Brooke escape a wrongful execution.
How does it all go down in the last episode? When Brooke and Donna make it to the camp, they find Margaret, who shoots Brooke. But Margaret doesn't get away with it — Donna lets the ghosts take her and grind her up into pieces.
In a flash forward to 2019, we find out she's now the medical director at Red Meadows Asylum, where Bobby tracks her down for answers about his father. She tells him Mr. Jingles was innocent and framed by Margaret. But Bobby offhandedly mentions he's been getting checks all of his life. Then, Donna, going on a trip with Bobby to find his benefactor, discovers Brooke is alive.
