Mopsa is a fairy, but don't presume you know what that means. Among other things, it means that as an infant, she is in danger of being eaten by a ferret. It means that she grows through childhood and adolescence like a human child -- but that may take only a few days. And it means that as an adult, she is a queen in the sense that some bees and ants are queens, and had better find herself a nest of her own before the local queen has to kill her.

All of this comes as a surprise to Jack, a human boy who takes her under his protection (and she needs it -- see above about predation upon fairy babies), but that is far from the only aspect of the fairy realm that is surprising and confusing to Jack, and Mopsa is not the only one endangered. Not to worry, though -- Jack returns to the mortal world alive and sound.