Did Kat kill Cliff?
In Episode9, we see Cliff sitting at the landry home writing a letter to Fern. He was happy with her and he wasn't going to the NYE party. Then Kat comes in and says something about "Will you be there? You usually are" and it worried Cliff, which made him go to the party, taking him to get Elliot arrested. All of them head into the tunnels.