Monster is a gothic fairytale set in a world of mythical creatures and monsters, and follows a little aquatic monster Cath as he struggles with thinking he's turning human.

Due to the micro-aggressions of the people around him, he starts to see parts of himself turning human in the mirror, and starts to freak out.

Piece by piece, he tries to hide them, going to ridiculous lengths to stay the monster that he is...

... Until all he sees staring back at him in the mirror is a little, disfigured human boy.