Gregory's Son of a Witch starts as a story of the past and present of Liir, which intertwines together to form the tale of his adventures. In the story of his past he finds that he has no where to go, and no one to rely on. He is completely alone in the world and takes to wandering the streets.

Flashing forward, he is in critical condition at a mauntery that he had previously occupied as a young child with Elphaba, The Wicked Witch of the West. Sister Doctor and Sister Apothecary do not know what to do for him. They do not know how he got to his state of broken bones and numerous bruises. It seems that he fell from a great distance, but they do not know how he could get to such a height.

The young Liir wants to find his possible half sister...