奥地利皇储突然自杀案件，让沉寂6个月的福尔摩斯（小罗伯特·唐尼 Robert Downey Jr. 饰）再次启动。这次，福尔摩斯有了一个强有力的对手——智力上与福尔摩斯相当的莫里亚蒂教授（杰瑞德·哈里斯 Jared Harris 饰）。为了调查清楚皇储的自杀案件，福尔摩 斯与华生（裘德·洛 Jude Law 饰），在吉普赛占星师西姆（劳米·拉佩斯 Noomi Rapace 饰）的帮助下，和莫里亚蒂展开了在整个欧洲大陆上的较量，从英国到法国、德国……虽然被称为最聪明的人，但是莫里亚蒂教授仿佛能预知福尔摩斯的行踪，都能先一步福尔摩斯逃之夭夭。莫里亚蒂教授死亡名单上的人一个个被抹杀，历史可能就此被改编，面对如此强大的对手，福尔摩斯如何应对？

After a four month absence, Sherlock Holmes returns to Baker Street following several attempts on his life. Holmes had been away on an important assignment for the French government - recovering the Mona Lisa that had bee stolen from the Louvre. He was successful in his task and appropriately rewarded by the French but he raised the ire of the crime's perpetrator - Professor Moriarty. On the morning of his return, the Professor visited Holmes in his flat and warned him to cease or he would have no choice but to take extreme measures. With several attempts on his life having already taken place, Holmes and Watson head for Switzerland. Moriarty is a relentless pursuer however and he and Holmes have a fateful encounter at the Reichenbach Falls. Written by garykmcd

第二季第一集承接上一季最后一集的剧情，从被炸弹和狙击枪威胁的夏洛克(本尼迪克特·康伯巴奇 Benedict Cumberbatch 饰)和华生（马丁·弗瑞曼 Martin Freeman 饰）和莫里亚蒂(安德鲁·斯科特 Andrew Scott 饰)第一次正式会面开始。 接着夏洛克在接受白金汉宫一份重要委托的案件中遇到了亦正亦邪的神秘女子艾琳·艾德勒(拉娜·普尔弗 Lara Pulver 饰)，一位旗鼓相当的对手，一个使他心动的女子。这一次莫里亚蒂使大众相信夏洛克所有的事迹全是虚构，使之变成一个伪英雄名誉扫地。而为了彻底打垮夏洛克迫使他跳楼，莫里亚蒂竟立刻吞枪自杀，结局到底如何，夏洛克会因此中了他的圈套吗？精彩尽在第二季。

本季延续《神探夏洛克第二季》的剧情，在莱辛巴赫坠楼案两年后，华生（马丁·弗瑞曼饰）努力让生活重新步上正轨，集美丽与智慧于一身的玛丽·摩斯坦（阿曼达·艾宾顿饰）将与华生一同步入和谐浪漫的人生新阶段。然而此刻，夏洛克（本尼迪克特·康伯巴奇饰）却上演复活戏码，虽然这是华生祈祷已久的愿望，但当愿望实现时，他还是无法坦然面对一切。这一次，夏洛克和华生需要解决伦敦街道下神秘的阴谋、婚礼上突如而来的意外，及面对恶名昭彰且阴险的勒索之王——查尔斯·奥古斯都·马格努森（即原著米尔沃顿，拉斯·米科尔森饰）。夏洛克回来了，但一切还和以前一样吗 ？

天文学知识空白、文学知识空白、哲学知识空白、政治学不及格--这就是歇洛克·福尔摩斯。可是，这又有什么关系？对这位世界上最伟大的私家侦探来说，能否完成缜密绝伦的推理、能否厘清最扑朔迷离的案情、能否破解最匪夷所思的案件、能否挑战最惊险刺激的冒险……这些，才是真正值得他关注并能给他带来无限快感的东西。讹诈、勒索、谋杀、离奇命案……这一次，声名显赫的歇洛克·福尔摩斯仍将叼着他的老烟斗，一脸精明悍练的表情，带领我们步入又一个惊心动魄、神秘诡异的历险之旅……

Sherlock Holmes is hired by the King of Bohemia to retrieve a compromising photograph from a certain lady. The King has tried to purchase the photo and even hired burglars to retrieve it, but without success. The woman in question is the very beautiful Irene Adler, an opera singer. She has made no demands of the King so it does not seem that blackmail is her intent. Using various disguises, Holmes learns as much about the woman as he can and is surprised when, after following her to a church, finds that she has married a barrister. Holmes stages a bit of theatre to get her to divulge the location of the photo but he finds he has met his match in both daring and intellect.

A gentleman is baffled when the childish drawings of little dancing men terrify his American wife. Sherlock Holmes soon discovers why.

An unknown thief steals an important naval treaty from the office of Mr. Percy Phelps, a Foreign Office clerk. Phelps's distress gives him a brain fever that lasts for nine weeks. As he begins to recover, he writes to his old schoolmate, Dr. Watson, begging him to invite Sherlock Holmes to investigate the matter and find the treaty. Otherwise, his honor and happiness are gone forever. Holmes takes up the case with zest, but gives Phelps no false hopes. The mystery is as dark and tangled as any he has known.

Col. Barclay is found dead and his wife is arrested for the murder, but Holmes is convinced a missing door key will reveal the true killer.

凌晨，诺伍德发生大火，富有的户主一位当地有名的建筑商尸骨无存。
火灾现场的大致情况如下：卧室的床无人睡过。保险柜门敞开，有激烈格斗的迹象，有少量血迹及沾血的橡木手杖一根。之前曾上门拜访建筑商的年轻律师成为最大嫌疑人并被警察逮捕。当然，福尔摩斯有他独到的见解，他坚定地认为：凶手另有其人，而且他已经找到!

Dr. Watson is shocked to learn that his good friend Sherlock Holmes has a brother, Mycroft, and that they are on their way to meet him on an urgent matter. There they learn of the strange case of Mr. Melas, a Greek interpreter, who was roused from his sleep in the middle of the night and required to interpret for a man who was clearly being held against his will. That man was beaten, bound and not allowed to speak but only to write out his answers to the questions he was posed. Clearly his captors are trying to force him to sign a document and are also keeping his sister captive. When Melas is taken a second time to interpret, Holmes, Mycroft and Watson must move quickly if they are to prevent a murder. Written by garykmcd

A strange man on a bicycle follows a young music teacher as she bicycles on a lonely road to and from the city.

嗜酒成癖的恶魔般的丈夫，天姿国色的天使般妻子，忠心耿耿一心为主的仆人，曾经富丽堂皇而今陈旧衰败的庄园……毫无疑问，这是个理应发生点什么故事或事故的地方。
当格兰其庄园的优斯塔斯爵士被通条击例，血和脑浆溅满屋子时，故事开始了......

Sherlock Holmes is asked by Inspector Lestrade of Scotland Yard to assist with a most peculiar case. He has been investigating a series of break-ins in shops and private homes where all that happens is the destruction of a bust of Napoleon. The case includes murder when one of the burglaries also leaves an unidentified dead man on the front steps. Holmes realizes that someone is searching for an article hidden in one of the busts. Written by garykmcd

英格兰最优秀的预备学校里，公爵大人的独子与一位德语教师神秘失踪，3天后，德语老师的尸体在学校附近的荒原被发现……
最令人疑惑不解的是，德语教师遇害的荒原附近一头牛也没有，路上却有大量牛蹄的痕迹…