What is the Secret? Actually, there's more than one—and the answers are revealed here. The true identity of Mockingbird was only one of the secrets, and it's not even the most shocking. Plus: A marriage that should not happen is proposed. A personyou thought was long gone returns. And at least one of the Six is not the person you think they are. (Okay, it's the dummy.) From this point on, all bets are off.