Meet Rosetta Halloway, a kind and hardworking young adult with a curious streak and a love of gardening. In her backyard is a stone waterwell filled to the brim with black water. The fact that this well didn't previously exist there is one thing, but then strange noises start coming from within it, which prompts Rosetta to investigate. Out comes a mysterious mermaid, Galatea of the Well, who appears to be particularly interested in getting acquainted with her. So, what exactly is this piscine stranger's deal? Do you have the strength to find out?