When I first read the tales of Old Man Henderson it cracked me up. If you've gamed for any amount of time you've met That Guy. Maybe he showed up with a character concept that had nothing to do with the setting. Maybe he spent three sessions methodically dismantling every plot hook the GM laid down. Maybe he was just a power gamer who treated every NPC like a loot piñata. The Henderson Scale of Plot Derailment puts a number on that guy, and there's something deeply satisfying about that.
The scale itself is simple. It ranks player behavior from minor disruptions at the low end up through full campaign-ending chaos at the top, with Old Man Henderson himself sitting at the theoretical ceiling as the unit of measurement. Henderson, for the uninitiated, is the infamous character from a Lovecraftian Call of Cthulhu campaign. A deranged Scottish vagrant with a vendetta against the cult that stole his lawn gnomes. The GM reportedly quit the hobby for a while afterward. Henderson is the benchmark. Everything else gets measured against him.
What makes the scale useful is that it isn't really mean-spirited. It reads more like a taxonomy than a callout. There's a difference between a player who bends the rules and one who breaks the social contract, and the scale actually tries to map that out. Some of the lower entries describe behavior that's annoying but basically fine. The higher you go, the more it's describing someone who is actively working against everyone else at the table having a good time.
It's also just funny. The framing is absurd and the examples escalate in a way that feels earned. You find yourself nodding along thinking about specific people from specific campaigns, which is either comforting or alarming depending on how many of those memories you have.
It's a short read. If you've ever had a session go sideways because one player decided the plot was optional, this is worth a look.
