Watson meets with Captain Gregson's daughter, Hannah. Three pharmacies have been robbed in her beat. The detective on the case has a full plate and Hannah wants to solve the case.
A man comes up to a car stalled on the train tracks. He opens the car door and a bottle of vodka falls out. He pushes the car across the tracks. The guy isn't drunk, but dead.
The deceased is Garrison Boyd who was a professional doubter that Sherlock admired.
Detective Bell and Sherlock visit the Church of Atomcism. Sherlock accuses them of being a cult. He gets a member to give them photos. They find pictures of Boyd arguing with Collin Eisley.
Joan and Sherlock interview him.He wanted to buy a home, but the woman refused to sell. Boyd later accused him of making her believe her home was haunted.
Joan and Sherlock visit Mrs. Renfinzger. She says her home is haunted by her husband, Harry. She plays a tape of him talking, but Sherlock realizes the "ghost" is speaking Arabic. He finds a tunnel between her basement and her neighbors.
The terrorists dug up a transatlantic data cable, Ruby, that connects Europe and the United States. Sherlock believes Boyd stumbled onto what they were really doing and they killed him.
Hannah visits the brownstone. Watson noticed that in all three robberies the same candy vendor visited prior to the robbery. She has photos of the men who match descriptions of the robbers at the candy vendor's warehouse. She notes that the police will likely put the warehouse under surveillance to follow the drugs up on the food chain.
Sherlock ask Joan what she thinks of Hannah. He believes she is a middling detective, which upsets Joan.
Sherlock finds the video with the suspect. He noticed a woman acknowledge the man. He visits her at her apartment. She says it is her neighbor. Sherlock realizes he overheard the conversation and is dousing his apartment with gasoline. Sherlock sets off the fire alarm and breaks into the apartment.
Sherlock has the contraption that Nadim was building to attach to Ruby. He believes it was mean to capture and transmit data to another site.
Bell tells Joan that Gregson is getting teased about Hannah being a chip off the old block with her arresting the pharmacy robbers.
Nadim's apartment is owned by Collin Eisley. They interview him again. He changed his name after doing time for insider trading. He says everything is in a blind trust.
Joan confronts Hannah and asks her why she didn't pass the information. Hannah says the detective would have made her a footnote.
The contraption doesn't transmit date. In fact, it doesn't do anything.
Joan ignores a call from Hannah. She admits that Sherlock was right. He tells her to not embroil herself further into Hannah's drama.
Sherlock realizes the contraption was meant to delay the big brokerage houses so that Eisley's broker could get the information first. He paid Nadim with a Picasso, which he won't be able to sell.
Gregson apologizes to Joan for Hannah. He tells her not to help her again. She needs to do better by herself.