When Cam shares his Mako Island research with Erik, the pair head out to the reef by themselves to investigate his findings. However, while diving with Cam, Erik touches a symbol engraved into a rock and is suddenly transported into an empty void. Cam rushes back to inform the others who return and begin a frantic search of the island for Erik. Ondina's feelings for merman Erik have caused a rift in her relationship with Mimmi but with Mimmi holding the key to rescuing Erik, will she agree to activate the merman chamber to do so? Meanwhile, Sirena searches for a new look to match Cam's new musical stylings.