A fan of the Hey Arnold! series, during a spout of nostalgia, discovers a lost episode of the series which was seemingly a draft of the episode "On the Lam," only he discovers that something more sinister is behind it. The story can be read here.
The Furnace provides examples of:
- Adults Are Useless: Grandpa Phil at first believed that Arnold was playing a game with Harold and Sid, failing to realize that his grandson was in grave danger.
- Dark Fic: Blatantly so.
- Downer Ending: Grandpa Phil ambiguously discovers Arnold's mutilated remains in the eponymous furnace.
- Driven to Suicide: Sid commits suicide out of guilt for taking part in the murder of his two friends, and Harold himself also kills himself after realizing too late that it was all a misunderstanding.
- Family-Unfriendly Death: As per usual for a Creepypasta. Stinky's head is repeatedly bashed in with a rock, Arnold is torn to pieces by Harold and Sid and his body parts disposed of in the furnace, Sid stabs himself out of remorse, Harold hangs himself, etc.
- Gory Discretion Shot: The story leaves the exact way that Arnold is killed out, just going into the aftermath of it.
- He Knows Too Much: Arnold is killed after Sid revealed that they murdered Stinky.
- The Hero Dies: Arnold is killed by Harold and Sid as a means of covering their tracks.
- Lack of Empathy: At first, Harold was apathetic towards committing murder if it meant escaping from the consequences, but this changes towards the end.
- My God, What Have I Done?: Harold and Sid both commit suicide after murdering their two friends.
- Oh, Crap!: Arnold has this realization prior to being killed.
- Poor Communication Kills: Arnold and Stinky die shamefully because of a mistranslation on the building being scheduled for demolition.
- Troubling Unchildlike Behavior: Harold is quick to suggest murdering Stinky and Arnold in order to avoid punishment.
- Your Head Asplode: Stinky's head is destroyed by Sid continuously bashing his face in with a rock.