As Ben and Gwen quarrel in the RV, Max nearly hits a boy in the middle of the road who they discover is a camper at nearby Camp Opinicon. Taking the boy back to the camp for treatment from his injuries, they discover the camp abandoned and after exploring come across two young twins who are campers. Soon they realize why the camp is abandoned when Max comes gets snatched up in the stalk of a gigantic fungus uncovered by some excavation work the camp was doing. Ben follows suit when he attempts to rescue his grandfather while Gwen, the boy they almost hit and the twins do their best to fight off the mutant fungus overtaking the camp.
The episode, from season 2 of the Cartoon Network show, originally aired on June 21, 2006.