A sequel to iNGO, this story starts out very confusing for someone who hasn't read iNGO. Sapphy and her brother, Connor, are part Mer (merfolk) and can enter Ingo. Ingo is a hard concept to define - it is a place, but not a place. It can be here and there. It is almost like the spirit of the ocean. Danger comes in the forms of the tides - which will escape the "knot" that keeps them contained in the oceans. Sapphy and Connor are instrumental in saving the world from destruction. There is a subplot with Sapphy and Connors father, who disappeared and is presumed dead by most. Sapphy discovers that he has turned Mer and later both Sapphy and Connor discover that their father is not captive as they thought, but is with another woman and has a new child - both Mer. This book slowly pulled me in, but I don't think that it stands alone: besides being very confusing in the beginning, there is a lot of foreshadowing that doesn't lead to anything, there wasn't enough build up to having to save the world, and I vote Nay for TU.