Caleb is visiting Gage's grave to tell him that he forgives him for what he did to Merlyn since he knows he was drunk that night. He doesn't seem to mean it since he just dumps the bouquet of flowers on the grave. Merlyn is in the back and when she sees this, she tells Caleb that it is important to forgive since anger only sprouts violence. Caleb tells her he finds it is still difficult to forgive Gage.
After Caleb leaves, Lucas appears behind Merlyn and asks her has she forgiven him. She tells him she never will and when he tries to throttle her again in anger, she throws him back using her powers. After she disappears, Lucas gets up but then kneels down again and starts summoning the powers of the darkness to send forth "the one."
"The one" turns out to be the dead Boston Strangler, Albert de Salvo. Lucas asks him to kill Merlyn for him because if a ghost is killed by another ghost, then that ghost will become oblivion. Lucas advises him that the way to get to Merlyn will be thru Caleb; that he must get Caleb to draw her out. De Salvo takes on the contract and tells Lucas he won't be disappointed.
Lucas leaves for a sheriff's convention the next day; putting Ben in charge.
De Salvo first disguises himself as a janitor at a hospital to spy on Caleb. He sees Caleb speaking to a nurse called Sarah so when he later on disguises himself as some sort of refrigerator inspector, he tells Caleb that Sarah had told him Caleb's name when he asked for the boarding house. This name-dropping gains Caleb's trust enough to let de Salvo into the boarding house. De Salvo further earns some points with Caleb by letting him help out with the refrigerator repair. But instead of repairing it, he cuts a hose instead purposely so that he can come back later.
That night, after the nurse Sarah has arrived home, de Salvo appears on her door and tells her he's a delivery man and was told to deliver some drugs to her. She tells him he's mistaken and that he should deliver it to the hospital but the hospital is closed right now. but he really needs to go somewhere early tomorrow morning so he can't go back to the hospital so if she could only sign for them, he'd really appreciate it. She ends up believing him and lets him in. As she is signing for the drugs with her back turned to him, he picks up a pantyhose she had dropped on the floor and strangles her with it.
As Sarah's body is being sent away the next day, Ben tells Floyd that he wants to keep a lid on the crime so as to not send everyone in town into a panic before they even know the details of it. Floyd insists that it must be murder since she couldn't strangle himself but Ben just wants him to keep his mouth shut about it until more evidence is found. Floyd is unable to find Lucas and worries that they can't handle all this; he wants to just seal the crime scene and wait for Lucas to come back. Angered, Ben admonishes him and tells him that he's in charge right now and he has to do what he says.
At the station, Gail drops in to try to get some facts about Sarah's death but Ben refuses to tell her anything. She wants to know if it was a rape but Ben just continues to hold her off. When he says that if Lucas was there, then she'll probably get the inside scoop, Gail slaps him and tells him that she keeps her personal and professional life apart and leaves.
While studying science in his room, Merlyn appears to Caleb and they start talking about sickness and death. Merlyn tells Caleb that it's not that bad being where she is but what is worse is to be in oblivion; "neither here nor there."
The next day, Caleb is again helping out de Salvo with the refrigerator repair. In the middle of it, Caleb mentions about his sister having passed away and de Salvo tells Caleb that he had a sister who had died the year before. Feigning sadness, he tells Caleb that he really misses his sister and would like to talk to her so he would really appreciate it if Caleb could ask Merlyn if she could help him. Caleb takes pity on him and says he will try. Gail comes in then and is a bit suspicious when she sees de Salvo, especially when he tells her his name. After he leaves, Gail tells Caleb that he shouldn't trust people so easily nowadays.
That night, de Salvo goes to Gail's house and tries to get in by imposing as a delivery man again. But Gail becomes suspicious immediately and she calls Ben without even looking out the door. As soon as she puts down the phone though, de Salvo appears beside her and starts attacking her. She does throw him off but then he reappears in front of her right after she turns away. He tells her that he is indeed the Boston Strangler and he's a ghost. He then takes one of her nylons and starts strangling her with it. Luckily, Ben arrives in time and starts breaking down the door when he hears Gail screaming. When Ben finally gets in, de Salvo has disappeared.
Gail tells Ben and Floyd later on about what happened but Floyd only thinks she's nuts. Ben is pissed off about this and tells Floyd to apologize to Gail and then leave. Gail tells Ben that her attacker told her he's the Boston Strangler, but Ben doesn't believe that since he's suppose to be dead a long time ago. She mentions to him that she had seen him before in the boarding house.
While Caleb is fixing an old radio, Merlyn appears and starts talking about how she has a strong sense of foreboding; something bad has arrived in town. They start talking about nurse Sarah who was killed for Caleb feels really bad about it. Merlyn tells him he should not blame himself since it definitely is not his fault and then warns him that she feels the danger coming very close.
Meanwhile, Gail and Ben are calling the boarding house but no one is answering. When they go over there, Caleb is nowhere to be found. Ben assures Gail that he's probably gone out to a friend's house and she needn't worry since the Strangler's victims have been women.
It turns out that Caleb had gone to the hospital to look for Gail after receiving a call that she was checked in. He finds out from a nurse that she never came in and as he is heading out, de Salvo calls to him from a storage room. Caleb wonders why he is there so he explains that he's just doing some work and he apologizes for making the false phone call so that he would come down to the hospital. Caleb becomes extremely suspicious and demands to know what he wants. De Salvo wants him to summon his sister and when Caleb refuses, he grabs him and demands that he does. Fortunately, Caleb is able to break free.
After he leaves, Merlyn appears behind de Salvo and tells him to leave Caleb alone since it's her that he wants. Del Salvo is a bit taken with Merlyn and even offers to team up with her to go against Lucas; even tho he doesn't really mean it. Merlyn of course doesn't fall for his charms and tells him to leave Trinity. He replies that he's not going to until he finishes his job here, to kill her. She uses her powers to attack him like she had attacked Lucas, but there doesn't seem to be any big effect on him. She then disappears before he could hurt her.
He starts cursing at her which draws the attention of a nurse. When she goes into the room to ask what's going on, he closes the door behind her and that's basically the end of her.
Ben is poring over the case files when Floyd comes in to tell him the lab said there were no fingerprints found. He expresses doubt in Ben's abilities which really gets Ben riled up. He really chews Floyd out and tells him if he wants to solve the case, they have to work hard. Just then a telephone call comes in and they receive the news about the nurse's death.
Back at the boarding house, Caleb is talking to Gail about how worried he was about her. She's touched and promises him that the Strangler won't hurt him or her anymore.
Back at the station, Ben and Floyd are both looking thru profiles of killers in the past and when Ben sees the picture of the Boston Strangler, he hurriedly goes on his way over to the boarding house, thinking it's a copycat.
As Caleb is reading in his bedroom, his toys suddenly takes on a life of their own. He then hears and sees someone approaching his room from the crack at the bottom of his door so he hides under the bed. The shadow then moves away but when he crawls out from the bed, de Salvo is already sitting on it, waiting for him. He approaches Caleb menacingly and tells him to call his sister. Caleb starts yelling for help and Gail hears him from downstairs. She immediately rushes upstairs and tries to go in his room but his door is locked. After pounding on it for awhile, she rushes downstairs to look for the spare key and to telephone for help. She finally finds the spare key so heads back upstairs; however the key doesn't help and the door is still locked. Ben joins her shortly and the two of them try to break thru.
Inside, de Salvo pulls out a knife and threatens to hurt him but Merlyn appears in time to stop him. She tries using her powers on him but still no avail; so she allows him to strangle her so that he would go away and leave Caleb alone. Caleb hollers for him to stop and suddenly, while Caleb is screaming, de Salvo is thrown across the room and his spirit begans to burn until he disintegrates. Caleb runs over to Merlyn who is amazed and sad at the same time because she tells him he used his force to help him which is the same force that will destroy him later on. She disappears when Ben and Gail are finally able to break open the door. When asked what happened to the attacker, Caleb only replies with an "I don't know."
The next day, the station is bustling with busy activity regarding the case. Lucas returns to find Ben actually taking charge and telling people what to do and explaining the situation to other officials over the phone. He is amused by all this. Floyd even tells Lucas that Ben did a good job when he was gone, but Lucas basically tells him to shut up. He dismisses Floyd and then tells Ben about how he won the award for Best Sheriff again. He shows Ben the award then goes into the office. Ben simply tosses it on his table with a unimpressed look.