While doing some research on Mako Island, Lewis uncovers the work of Max Hamilton, who, fifty years before, was also investigating the place. Realising that his findings could be the key to finding out more about the Moon Pool and the girls' transformation, Lewis tries to befriend the old man, but finds him unwilling to talk - until, that is, he sees Cleo talking to Lewis, and recognises the locket around her neck. Max follows Lewis and Cleo to Mako Island, splashes some water on Cleo, and discovers that she is a mermaid as well. He is not shocked, however, because Max was a friend of Miss Chatham's when she was a mermaid along with Gracie and Julia Dove in the 1950s, and was romantically involved with Gracie. Max promises to keep Cleo's secret, and hands his research on Mako Island to Lewis.