Diane Stanley - The Cup and the Crown (Silver Bowl #2)

Molly explores the source and nature of her ever-changing magical gift. Sent by king Alaric on a crucial mission, she is drawn to Harrowsgode, the mysterious walled city where her grandfather was born and from which he later escaped. What she discovers there will alter the direction of her life and challenge her considerable ingenuity and courage. With the help of Tobias, a rat-catcher named Richard, and a clever and devoted raven, Molly gains her own freedom in a most unexpected way, and changes the city of Harrowsgode forever.