Knight and Daye Series

A mysterious handprint appears on an aquatic fishtank, which is part of an exhibition showing off many species of fish, including the Mercastes, who are half-fish and half-human beings.  They are a curious sort, and one in particular comes up to this handprint, which was placed on the tank by a young Mortal lady.  The Mercaste is intrigued by this, which had imprinted on his mind, and by the lady who put it there in the first place.  Can this mythological being overcome Mortal prejudice to meet her?