"Well, the walls between worlds are firm now. One can only pass through them by meeting certain regulations. First, they must have a token of the world they are moving to, the next down the line. Red and Gray are close to each other. And she was with my brother, plenty of tokens there. And the other thing is the power of an Antari blood mage."

Which Kell was. And it turned out she was.

"She followed him home, like a lost puppy, this little woman who was a thief in London. And proceeded to crash my birthday party."