A man is killed in a parking garage before work. He has ripped skin and bite marks, as well as a co-worker who swears they were attacked by zombies.
The victim had been having an affair with an engaged woman.
An underground group goes on “zombie walks” as part of a game. The fiance of the engaged woman sells a drug known as the zombie drug to those involved to give a more realistic experience. The drug causes the person to forget what they did and do as they are told. The fiance convinced one of the zombies to kill the victim to get him out of the way for his marriage.
Castle and Alexis carry on their laser tag game. Alexis chooses to go to Columbia for college.
Castle wants to make this his last case until she tells him she has been going to therapy and working to break down that wall.