Co-creator Tim Minear tells TVLine that Britton's “Abby promised she would come back and she never did. So there’s unfinished business for Abby, and definitely also for Buck. He’s kind of lost at sea right now. He’s still trying to figure out who he is, and his relationship with Abby started to redefine him. Once she left, he had to figure out who he was without her.” ALSO: 9-1-1: Lone Star doubles down on 9-1-1's tragedy porn with Rob Lowe playing "Firefighter Rob Lowe."