Lonely, Velma investigates a anonymous tip about “Fish Freaks” haunting an abandoned Destroido oil rig. She is attacked by the Fish Freaks, and discovers a mermaid called Amy sent the tip. Velma enlists the help of the gang, only for them to get captured. They discover the Fish Freaks are attempting to drill for oil, which would cause a major environmental disaster. The gang stops the Fish Freaks, who are revealed to be Ernesto and the activists, who wanted to sell the oil to fund their projects. Amy reveals herself to be human. She went in disguise to get Velma to help rescue her husband, who was kidnapped by the Fish Freaks. Thanks to her, Velma realizes Angel is not who she says she is, but is instead Cassidy Williams of the original Mystery Incorporated.
