The second season starts on the same point at which the first one had finished; with the cliffhanger at the pool. The standoff between Sherlock and Moriarty is interrupted by a phone call to the latter. Moriarty claims to have gotten a better offer & lets Sherlock and John leave alive. In the following weeks Sherlock becomes a minor celebrity after John blogs about his activities. During the investigation of man who died in the countryside, Sherlock & John are called to Buckingham Palace by Mycroft. He and a palace official reveal that Irene Adler (Lara Pulver), a dominatrix known professionally as “The Woman”, took compromising photographs of her and a female member of the royal family, and wants the pair to retrieve her mobile phone on which the photos are stored. This is after Sherlock goes through a hilarious episode when he is naked without his robe. Using deception the duo makes their way into Ms. Adler’s home but it seems that she was expecting them and appears naked in front of them – so Sherlock is stumped and cannot educe anything about her!
Very soon CIA officials led by Nielson break into the house and demand that Sherlock open the safe, which he does after realising the combination is Adler’s measurements and opens the safe, which is booby-trapped with a handgun that kills one of the assailants. After the rest are disarmed, Sherlock takes the phone which also contains other valuable information. However, Adler sedates him and steals the phone back before escaping. Sherlock later wakes up in his bed to find that Adler tampered with his phone, by adding a personalised ringtone of Adler sighing erotically whenever she sends him a text. 6 months pass and Adler sends Sherlock her phone (which requires a code that he does not know to unlock), and he realizes she will be found dead; her mutilated body is later found and identified. However John is contacted by someone, who he thinks is Mycroft, and goes to an abandoned power station, and runs into Irene Adler instead! She had faked her death to shake off the people who are out to kill her for the phone. Sherlock, who followed John, also sees that she is alive. Sherlock returns home to find that Nielson’s team are making another attempt to take the phone, by imprisoning his landlady Mrs Hudson. Sherlock tricks and overpowers Nielson, and throws him out a window. Later on, Adler reveals that she is still being hunted and asks Sherlock to decipher a code she stole from a Ministry of Defence (MOD) official. He effortlessly cracks the code, revealing it to be an airline seat allocation number. Adler secretly texts the flight information to her contact, Moriarty, who in turn texts Mycroft, revealing that he is now aware of the MOD ploy to fool a terrorist cell that was attempting to bomb a plane.
Adler then attempts to seduce Sherlock but they are interrupted by government officials who take him to Heathrow airport. His suspicions that a similar situation to that during World War 2 is occurring are confirmed by Mycroft; the US and UK governments have decided to fly a ‘dummy plane’ full of corpses so as not to alert the terrorists while avoiding casualties. However, as Sherlock unwittingly helped Adler and therefore Moriarty crack the code, the scheme was foiled. Adler reveals a list of demands to Mycroft, including protection, in exchange for the release of the information on her phone. Adler further taunts Sherlock by revealing that he meant nothing to her. However Sherlock realizes she is lying, as he previously took her pulse that proved otherwise. He opens the phone with the password “SHER” (so that its screen reads I am Sher-locked). With her leverage gone, Adler pleads for protection, as she is unlikely to outrun her enemies, but Sherlock and Mycroft turn her down. Some months later, Mycroft informs John that Adler has been beheaded by a terrorist cell in Karachi, Pakistan, but asks him to tell Sherlock instead that she has entered a witness protection program in America. Sherlock appears to accept this and asks John to give him Adler’s phone. After John leaves, it is revealed in a flashback that Sherlock actually went to Pakistan to pose as her executioner, revealed himself to her, and rescued her.
A lot of fun, perhaps the best episode of the bunch so far.