The episode begins with a man arriving home. He goes to the bar and pours himself a drink, completely unaware of the fact that there is stranger sitting on a couch with a laptop. The stranger clicks a button, and the man has an attack. With the click of another button, he man feels better. The stranger makes the man aware of his presence and tells him that he is able to control his pacemaker through his laptop. He explains that every pacemaker has a unique code and if one knows that, he can make the pacemaker do all sorts of things. The man asks the stranger what he wants. The stranger tells him to cast his ballot, vote to revoke. The man does the same.
The stranger thanks him, and kills him with the click of a button. In the prison, Sebastian Moran watches the news and learns that the Philanthropist, Philip Van Der Hoff, died of a heart attack. At home, Holmes manages to get himself inside a straightjacket and ends up dislocating his arm. Watson fixes it. Gregson calls and tells Holmes that Moran is ready to give them the names of the victims he hasn’t revealed, but he would give those names only to Holmes. Holmes goes to meet Moran. Moran tells him that he received a coded text from Moriarty, along with Philip’s face. He feels that Philip was killed. He tells Holmes that if he finds Philip’s murderer, he would be one step closer to Moriarty. He also tells Holmes to be quiet about this. On his way out, Moran deliberately attacks the guard.
At the precinct, Holmes tells Gregson that Moran called him to threaten him, and on his way out, attacked the guard. Gregson doesn’t find it too convincing. Watson figures out that Holmes is lying. Holmes tells her the whole story. Philip was a middle aged man with a known heart condition, so there was no autopsy. His body was directly sent to the mortuary. So, Holmes and Watson break into the mortuary. Holmes finds some marks on the palms which indicate that Philip clenched his fists really hard before he died. Watson explains that this action is not consistent with a heart attack; it is more consistent with electrocution. Holmes decides to do an illegal autopsy. Since he is unable to, Watson dissects the body.
Watson takes a look at the heart and tells Holmes that it looks like the victim’s blood boiled. At home, Holmes finds out that the pacemaker can be hacked and it can be used to send enough voltage through the heart, leading to a heart attack. The next morning, Holmes tells Watson that in addition to being a philanthropist, Philip was a member of Landmark Protection Council. The Council was currently reviewing the status of Taggart Speakeasy Museum which is owned by a Shell company. The site owners wanted to have the landmark status removed which would free them to redevelop the site. Holmes states that over the time, more and more Councilmen revoked their votes, and shortly afterwards, applied for home remodeling permits.
He says that all the renovations were handled by Robert Baumann. It is weird that a man who builds skyscrapers, agreed to do small renovations. Holmes also tells her that the last thing Philip did before he died, was change his vote on the Taggart Speakeasy. Next, it is seen that the stranger who killed Philip, kills Robert Baumann by dropping an air conditioner on him from a building. The stranger waits by a window for Robert to show up, starts the stopwatch, a girl runs into Robert and the stranger drops the unit on Robert; perfect timing. Later, the team shows up at the recent crime scene. Holmes thinks that Robert was murdered, but Watson thinks that it requires a lot of precision, and so she thinks that it was Robert’s bad luck. At home, Holmes proves that it is possible to kill someone the way Robert was killed.
It looks like Holmes believes that Moriarty exists. Holmes feels that the murderer could be one of Moriarty’s agents, someone who is more skilled than Moran. Later, Holmes makes Watson watch Hillary Taggart’s interview on television. Hillary Taggart is the last living person of the Taggart family and she fiercely advocates the preservation of the Speakeasy. Holmes tells Watson that whenever the existence of the Speakeasy is threatened, Hillary creates a nuisance by threatening to file law suits or through some public stint. Holmes thinks that Hillary could be the next target. He decides to observe Hillary because the best way to save her, is by finding a way to kill her. They go to the park, where Hillary goes for her jogs.
Watson notices that she Hillary is wearing a medical bracelet while Holmes notices some kind of a bee that is not native to New York. Holmes goes in search of a beehive. Watson tells Holmes that Hillary might be allergic to something, which requires her to wear the bracelet. Holmes figures the way the killer has planned to kill Hillary. He takes Watson to a hive and tells her that someone has placed these African honeybees here, so that he could poke a stick into the hive the moment Hillary goes for a jog. He tells Watson that the killer is feeding the bees with sugar water so that they multiply faster. He also knows that the killer will swipe Hillary with lemongrass so that the bees are attracted to her. They decide to stakeout the beehive because they know that the killer will come to refill the sugar water since it is getting over.
At night, they see a man (the stranger) arrive at the park to refill the sugar water. Holmes takes away his notebook and tases him. At home, the stranger regains consciousness and finds himself in a straight jacket. Holmes tells him that he knows that his name is Daniel Gottlieb and he is a retired engineer. His notebook also proves that he killed Philip and Baumann, and that he works for Moriarty, who sends him coded messages. Holmes wants Gottlieb to arrange a face to face with Moriarty, or else they will simply hand him to the police. Later, Gottlieb decides to talk. He tells them that he has killed 31 people. He tells them that eight years ago, while he was working late one night, a tall, British guy came up to him and told him that he knows that he (Gottlieb) is a serial killer. He took Gottlieb for dinner.
He told Gottlieb that he had a knack to identify psychopaths. Gottlieb says that he never saw that man again, and they always talked over the phone. Holmes asks him about his employer. Gottlieb says that the employer never said anything much about himself. However, he did mention that he was in some reform school when he was a kid. Gottlieb also remembers getting a text with Holmes’ face, but later he received a message which said that the job was cancelled. Holmes receives a coded text wherein Gottlieb’s employer has agreed to meet. Holmes and Watson go to the decided spot and keep a watch at the people in the restaurant. A young guy looks pretty nervous about the fact that he got stood up. He leaves to report to the guy who assigned him the task.
The guy meets the employer on the other side of the tracks. The train arrives, and Holmes clicks a series of pictures through the gaps in between the moving train. At home, Holmes manages to get the picture of the man who took Gottlieb out for dinner. He learns that the man is John Douglas. He tells Watson that Douglas was a brilliant kid and he did go to a reform school in England. He was also suspected in the murders of three guys at school, but since last 45 years there isn’t a whisper about him in the systems. The next day, Holmes manages to find Douglas, and goes to meet him in his hotel room. Douglas tells him that he is not Moriarty. He also tells him that Irene had to die because of him, but before he could say anything further, somebody shoots him through the window.
Later, Gregson and the unit arrive at the crime scene. Holmes tells him everything about Gottlieb. In the interrogation room, Gottlieb admits to the murders he committed. There is a new message in Gottlieb’s inbox. Holmes checks the message and asks Gottlieb to decode it. Gottlieb does not recognize this code. Holmes meets Moran in the prison and asks him to decode the message. Moran doesn’t tell Holmes anything and goes back to his cell. At home, Holmes manages to crack the code.
It is a message for Moran which says: Moran you never told me you had a sister. She dies or you do your choice. M. In the prison, Moran bangs his head repeatedly on the mirror. Holmes warns Gregson that Moran might try to commit suicide, but it is too late. Moran is dead. Holmes is upset because Moriarty played him into taking the message to Moran. The phone rings. It is Moriarty. The episode ends.