Trama

In this rewritten version, Sherlock Holmes does not criticize an accused murderer's grammar or refuse to help him. Instead, he is engaged in a different case. John receives news of an explosion on Baker Street while visiting his girlfriend Sarah's apartment. Upon returning home, Sherlock and his brother Mycroft are seemingly unaffected by the incident. Mycroft urges Sherlock to investigate the murder of MI6 employee Andrew West, who was found dead on a railroad track. The case involves a missing flash drive containing defense missile secrets, suspected to have been taken by West. Despite Mycroft's request, Sherlock initially declines to take on the case.

Later, Sherlock is summoned to Scotland Yard, where he is presented with a phone resembling the one owned by a murder victim in a previous case, "A Study in Pink." The phone plays five Greenwich pips and displays a photo of the basement flat in Sherlock and John's building, along with a pair of trainers. A frightened woman calls, relaying a message from an unknown third party. She informs Sherlock that she is wearing an explosive vest that will be detonated unless he solves a puzzle within 12 hours. Sherlock deduces that the five pips indicate he must tackle five challenges.

While Sherlock and John examine the trainers, they are interrupted by Molly Hooper, a lab tech who has a crush on Sherlock. Molly introduces her new boyfriend, Jim, who works in IT. Sherlock deduces that Jim is gay and openly expresses his observation. The trainers belonged to a schoolboy named Carl Powers, who drowned under mysterious circumstances. Sherlock, who was underage at the time, had been interested in the case but failed to convince the police. Now, using clues left on the sneakers, Sherlock deduces that Carl Powers was poisoned through his eczema medication, although the identity of the poisoner remains unclear. The trapped woman is subsequently freed.

A second message features a sports car stained with blood. Another hostage provides Sherlock with eight hours to solve the mystery. Sherlock discovers a rental agency card in the car's glove box. By analyzing details such as the agency owner's distinct suntan and recent visit to Colombia, as well as the frozen blood in the car, Sherlock concludes that the missing man, Ian Monkford, paid the agency owner to help him disappear. Once again, Sherlock successfully rescues the hostage. He becomes convinced that his adversary in this battle of wits is the enigmatic Moriarty, the same individual referenced by the killer in "A Study in Pink."

Next, Sherlock delves into the death of Connie Prince, who supposedly died from tetanus after cutting herself on a nail. However, Sherlock determines that the wound was inflicted after her death. A blind woman calls, challenging Holmes to solve the crime within twelve hours. Sherlock uncovers evidence that points to the housekeeper as the murderer, revealing that she increased Prince's Botox injections to kill her. Despite solving the puzzle in time, the bomber triggers the explosives when the hostage starts describing her kidnapper's voice. Unlike the previous hostages who received messages via pager, the blind woman communicated with the bomber through a headset. The photograph of the River Thames is the fourth clue. Sherlock discovers the body of a security guard at the river, marked with bruises characteristic of "the Golem," an assassin. The guard had suspected a recently discovered Vermeer painting to be a forgery. An astronomy professor, who had conversed with the victim about the painting and left him a message on his phone, becomes another target. Although Sherlock and John fail to save her life, they find a clue that proves the painting is indeed a fake, thus saving the fourth victim. The museum curator discloses that the person ultimately responsible is known as Moriarty.

While investigating the Andrew West case on his own, John becomes perplexed upon learning that very little blood was found on the tracks. Sherlock agrees that West was killed elsewhere and then placed on the train's roof. They confront West's prospective brother-in-law, who confesses to stealing the flash drive and accidentally killing West.

Sherlock waits for John to leave and arranges to meet Moriarty. However, instead of encountering Moriarty, he is surprised by John, who initially appears to taunt him but then reveals himself as another hostage wearing an explosive vest and having his words dictated. Moriarty appears and turns out to be Jim, Molly's boyfriend. John attempts to apprehend Moriarty but releases him when a sniper aims at Sherlock. Moriarty leaves momentarily but soon returns, commanding multiple snipers to target both Sherlock and John. Sherlock aims his handgun at Moriarty but ultimately redirects his aim toward the explosive vest, which he had thrown across the pool deck. The episode concludes with this gripping cliffhanger.