The story of Grimalkin--Book Nine of The Last Apprentice series

Grimalkin never missed--except once. The only victim who escaped her blades was Tom Ward, a seventh son of a seventh son. Since then, the witch assassin has fought alongside the Spook's apprentice. Now you can hear her side of the story. What is Grimalkin's past--and what will her future be? Can Tom trust her to stay on the side of good? Or is the pull of the dark too strong to resist?