What, Will, I, Have, Left

The BAU has another run-in with Will while working a case up in Boston. Theo Jacobs has just been murdered, and his little sister, Tate, is left alone. Will and JJ decide to take her in, but what happens when Tate Jacobs isn't the girl they thought she was? The story of Will and JJ fostering a teenager before Henry is born. Starts after "In Heat" but before "The Crossing",