Robbie Amell, Hayley Kiyoko, Kate Melton, Nick Palatas, and Frank Welker cast reprise their roles.

He tells them the story of the lake monster: when people first settled in Erie Point, the witch Wanda Grubwort, who used moonstones as the source of her power, warned them not to come onto her land.

After they ignored her warning, she used her magic staff to transform a frog into a monster that attacked the villagers before she was tried for her crimes and burned at the stake.

The next day, Velma shows the group security footage of the lake monster meeting a mysteriously cloaked figure on the beach.

The situation is complicated by friction between Fred and Daphne, whose relationship has become strained due to them socializing with others and Shaggy's feelings for Velma causing him to alienate Scooby.

After they inform her of the latest monster attack, Daphne says that she saw purple paint on the figure's cloak and suggests that they check out a boat that they saw on their way to Erie Point.