After Deb learns that she has sent forensic evidence to an outside lab for analysis, Captain LaGuerta confides in her that she found a blood slide at the site of the Marshall killing and believes the Bay Harbor butcher is still alive. The Captain accepts Deb's offers to help her in the investigation. When Dexter learns what's going on, he just wants Deb to stay out of it. Dexter finds blood on his boat and tests reveal it belongs to Louis Greene. He soon after finds he has to deal with Isaak Sirko who is clearly out for revenge. Dexter's plan to get him doesn't work out. Hannah McKay meanwhile has agreed to help find some of the bodies from her and her boyfriend's killing spree years ago. The remains of one of the victims tells him a lot about the assailant.