The PCs must cross a forest that is fenced off for some reason. After crossing the fence they discover why there are Keep Out notices. The bushes are full of large and deadly looking brown spiders.
Unknown to the PCs, these spiders can give a nasty bite but are otherwise harmless. The real danger is the saucer-sized silver-furred trapdoor spiders in the soil. If a player steps on a trapdoor it will break and the spider within it will bite him/her on the ankle.
The bite has a narcotic effect and the player must make a Willpower check when he/she recovers to avoid becoming addicted to the venom.
There are criminals within the woods that are harvesting the spiders to feed their illegal drug trade and will see the PCs either as law enforcement or as a rival gang.
There are Sheriff’s men searching within the forest for the criminals who will see the PCs as a threat.
If the PCs dig up one or more spiders without getting bitten, they might choose to enter the illegal trade themselves.More honest PCs will just want to get out of the forest as quickly as possible. An addicted PC will try and get bitten again and must be healed in some way to avoid becoming a “spider junkie”.