William is the son of the owner of the travelling circus Hathaway's Cabinet of Wonders, considered the sole heir despite his father treating him with contempt and keeping him away from any important decisions. Of all the people working at the circus, he alone came to see the captured mermaid not as a curiosity but as a living, suffering creature, and so he began secretly coming to her tank in the evenings, talking to her and caring for her in a way no one else around did.