" And round and round and round. Why couldn't I get past the letter? Like poison id had seeped into every image and every memory I kept of Callum, polluting them until I couldn't tell which was real and what was just wishful thinking any more. Until at last, I was forced to face the inescapable fact that, for whatever reason, Callum had written the letter. "

― Malorie Blackman , Knife Edge (Noughts & Crosses, #2)