[citation needed] After Shaggy Rogers discovers he suffers from a disorder that causes him to irrationally overreact to frightening stimuli, he fears that he can no longer remain involved with Mystery Inc. His friends take him to a spa in the town of La Serena to help him calm down.

Hubley explains the ghost dinosaur was the "Phantosaur", which legend says was summoned by Native Americans to regain their land from European colonists, before hypnotizing Shaggy into switching between his regular personality and a fearless persona when hears a specific keyword.

As Fred, Daphne Blake, and Velma Dinkley investigate the dig site for dinosaur tracks and what appear to be snake trails, Shaggy fights a biker gang at a buffet and is invited to join a motorcycle race after hearing the keyword, "bad".

Meanwhile, Daphne, Fred, and Velma notice a van owned by the mining company containing cables and whose tires match the snake trails they found earlier.

They and the bikers soon flood the van, revealing the Phantosaur was an animatronic operated by someone they believe wanted to scare off Svankmajer's team so they can tap into a silver mine.

Svankmajer reveals her team had found a dinosaur skeleton preserved in quartz crystal and sought to scare off La Serena's citizens so they could claim it for themselves.

Though the paint strippers set off explosives that the paleontologists intended to seal off the mine with, Shaggy overcomes his fear and gets outside to gain help from Tex's gang in rescuing the others.