The fourth series begins with the nation’s favourite detective, the mercurial Sherlock Holmes, back once more on British soil, as Doctor Watson and his wife, Mary, prepare for their biggest ever challenge - becoming parents for the first time.

Sherlock Holmes and Dr. Watson find themselves in 1890s London in this holiday special.

本集因以电视电影形式报艾美奖评选而被单独列出，改编自原著《米尔沃顿》。华生受朋友请求来到一个年轻人吸毒聚集地，没想到在这里居然遇到夏洛克。华生把夏洛克带回贝克街，惊讶的发现夏洛克有了女友，这位女友正是自己婚礼上的伴娘洁琳。但随后华生发现，夏洛克之所以和自己的伴娘约会是因为在查的案件。夏洛克假装要求婚，混进了讹诈专家马格努森的办 公室，华生也和夏洛克一起，然而就在夏洛克发现马格努森被人威胁的时候，威胁者转过头，这个人竟然是华生的新婚妻子玛丽……

Sherlock is back, but will things ever be the same again?