The team are baffled when an eyewitness, fisherman Jeff Simmons, swears that he saw a legendary mermaid on the night a seaweed farm was sabotaged. With no logical explanation for how someone could sabotage the farm and get away unseen amongst glowing bioluminescent waters, Esther braces herself for an excited Humphrey to run wild with the possibility that their prime suspect could be a mermaid... though it's clear that something else is playing on his mind.
Investigating the nets used to sink the seaweed farm, the only clue Humphrey has to go on is a mysterious tropical shell, along with the discovery that the farm is looking to expand. Could it be a protest from angered environmental groups? A personal vendetta? Or is a vengeful mermaid out to stop those who threaten her seas?
Meanwhile, Humphrey and Martha's new house renovations get off to a bad start when Humphrey's attempt at plumbing leads to disaster. Increasingly distracted, Humphrey comes clean to Martha about the weight on his shoulders as Mr Smith ups the pressure from the Hub for his decision. Martha and Esther finally find the time to let their hair down and throw caution to the wind when their night out ends in skinny dipping. And Kelby continues to gush about his new online girlfriend, though Margo reckons she sounds too good to be true.
