Right off the bat in season four of 13 Reasons Why, Jessica Davis and Clay Jensen keep thinking they're seeing their dead classmates. Jessica sees Bryce Walker and Clay sees Monty de la Cruz, though both of them died in season three. Clay seeing Monty is particularly concerning, as it's all part of Clay experiencing dissociation as part of his trauma. Seeing dead people is one part of Clay's dissociation, and another is destruction, including vandalizing the school.
Students arrive at Liberty High one morning to find that someone has spray-painted a message on the school's main office door that says "Monty was framed" in bright red paint. No one knows who did it, but Clay, Jessica, and the rest of their friends start to worry that someone knows the truth about what happened in season three: Monty, who was killed in jail, didn't actually murder Bryce, even though the murder was pinned on him. Alex Standall is the real killer - and his police offer dad knows the truth - and this group of friends assume they're in the clear since Monty is dead.
But are they in the clear if someone knows Monty was framed?
Things get sticky for Clay when he gets harassing phone calls from Monty's phone number and a red can of spray paint shows up quite literally at his feet on the school bus, but Clay can't figure out who is messing with him. And though it turns out Diego and the football team are the ones spoofing Monty's phone number to mess with him, they aren't actually behind the graffiti.
Clay is the one who spray-painted the message in the school, and he figures it out after his therapist helps diagnose him with having dissociative episodes in which he does things he doesn't remember. After Clay is caught setting a car on fire at the school, his therapist helps him figure out what's going on, and one of the things Clay did while dissociating was paint the office doors with "Monty was framed."
And even though Clay graffitied the school, seemingly ready to blow everyone's cover without knowing it or meaning to, no one else ends up pressing Bryce's murder case, and it is put to rest.