The Golden Mean (Griffin & Sabine #3)

I can just hear the author in a meeting with the publisher: “Well, this series of works has been immensely popular. We've got to get at least one more book out of it, which will of course be a surefire hit.” “I know! How about this: We introduce the correspondence of a new, vaguely sinister character, who we just abandon at the end! Foolproof!”

Yep. I found this frustrating and pointless. Humbug.