This episode begins with the team investigates the aftermath of a killing, that included horses. Everyone is stumped but the new detective Mike Anderson was able to connect the killings to a biblical reference from the Four Horsemen of the Apocalypse.
The team compares with case to the previous case with the snakes. Dexter finds paper with a number written on it in two of the bodies, signifying that the murders happened 4 days apart. Masuka finds oxidized iron in the jogger which means that the killer may have used some ancient weapon to kill, possibly an sword from a university where the professor (Gellar) has been missing for years. Quinn and Batista get a lead on Gellar.
Travis starts seeing Lisa, a waitress. Professor Gellar is not happy with Travis' non murder related relationships going on. Gellar spies on them then tells Travis she'll be their next victim. Dexter and the team burst into a crime scene to see Lisa tied to a rope. As they open the door, the rope tightened. Dexter spies Travis outside of the crime scene looking braindwashed.
Harrison is rushed to the emergency room for a ruptured appendix. Brother Sam comes to the hospital to offer Dexter support. Dexter breaks down, praying Harrison will be safe. Dexter discusses the Four Horsemen killer with Sam. Sam tells Dexter that the religious implications could mean anything.