Tess is Amy's older sister, She is the 3rd human to find out about the girls' secret, and causes a lot of trouble because of it. She gets sent to boarding school, because her parents think she is crazy. At the school, her therapist convinces her she is crazy, and makes her forget about it... For a litle while.  While she is back home, she completly forgot about it, until she gets back home from the market. She looks for Amy to make sure she is just outside, or can't hear her or something like that. She walks outside, and sees the girl's tails, then she almost faints, and she runs up to her room, with bad memories of them being mermaids (she only remembers them while they had seen the sunset, and had gotten mad at her). Thinking they are murderers, she "swears she will get revenge on them"