Deb confronts Jordan Chase this week and shares with him her theory that a vigilante is killing all her attackers. She then gets a court order (with Laguerta's help) to ground Jordan in Miami, as he had planned a speaking trip through Europe.
But Jordan isn't on his private plane when she shows up to give it to him and viewers know why:
He's convinced Emily to call Lumen and get her to over to her place in order to calm her down about going to the police. Lumen leaves Dexter a message about this development and heads over there. Once she arrives, Jordan is waiting. He brutally kills Emily with a fire poker because he doesn't want any witnesses and then, we assume, he takes Lumen away somewhere. (His actions beyond killing Emily aren't shown.)
Where is Dexter this whole time? He realizes a camera has been planted in his apartment because the baby monitor picks up its signal. He then sees its property of Miami PD and uses the department's computer to discover Quinn checked it out. (We all know it was Liddy, of course). He then sees a parked van around his apartment and is prepared to grab up Quinn inside it, only for Liddy to taser him.
Dexter awakes in the back of the van, as Liddy calls Quinn to come down and make a bust or else he'll go to Deb with what he knows. After hanging up, Liddy tells Dexter that if he confesses on camera, something that will help Liddy get his job back, he'll keep Lumen out of it. But before this can happen, Dexter breaks free and kills Liddy. Just as he does, Quinn pulls up, but can't get into the locked van. He thinks it's empty.
However, a drop of Liddy's blood seeps out and lands on Quinn's shoe as he walks away and then drives away.
Dexter escapes, tosses Liddy's taped evidence into the water and then calls Lumen back. He leaves a voicemail and says he's on the way. When he arrives at Emily's, he finds her dead body and a lot of blood. He also finds a small knife he had bought Lumen. It's on the driveway and it has blood on it. The episode ends with him running off, desperate to find Lumen.