Whumpee who's kinda terrifying.
Now we can interpret this as they've been through so much that the current shell of their former self is haunting Caretaker.
The way they look at them with those hollow eyes, how they stay so eerily silent and still at times, how when they sleep they look like a corpse. How their chest isn't visibility moving while breathing, how sad they look while they trace their scars, how Caretaker sometimes finds Whumpee just sitting on the floor and feeling up their body. Hands around the neck and tracing the spine at the back and larynx at the front. Or maybe the eyesockets, a bit stiff fingers prodding the skin under their eye.
They forget to eat, they don't drink enough water, sleep comes rare, and Whumpee refuses to lay in bed, mostly hiding under it.
And the way they look at knifes in the kitchen. Caretaker isn't sure if Whumpee's being anxious about being hurt by them [knifes] or they plan on using them. And on who. Whumpee's terrifying, Caretaker starts walking on eggshells.
Caretaker can't get a full night rest anymore. They're not only worried about Whumpee, they're worried about their own life. And they don't know why. It's not rational, but one of them will die. It's just a matter of time. Whumpee's danger to everyone around them.
Or are they? So far they didn't show any destructive habits. They've just been different. Caretaker don't know what to think anymore. Presence of Whumpee alone makes them question everything. They knew Whumpee before, they know Whumpee's not violent. Never been. But after Whumper, everything is just.. wrong.
So when Whumpee suddenly leaves/disappears, Caretaker is ashamed to admit they're relived. Until few days later they see a blurry CCTV footage on the TV news, with the presenter talking about a suspect in a potential murder. And they recognise the hoodie the figure is wearing.