The Denman Affair

S1 E8: Lewis studies the girls and is on the verge of discovering how they transform into mermaids. It's all mind-numbingly boring to the girls until Lewis meets a charismatic newcomer, Dr Denman. She's a drop-dead gorgeous marine biologist and Lewis is tempted into telling her too much about his friends' secret. Cleo is immediately jealous but when Denman steals Lewis' samples, the mermaid secret comes under threat. Will Lewis abandon his friends and risk their secret, all in the name of science?