Sherlock: Every Episode Ranked Worst To Best
3. Season 3, Episode 3: His Last Vow
After relying so heavily on Moriarty, Lars Mikkelsen's turn as the vile Charles Augustus Magnusson feels like a breath of fresh air, and crucially felt like something very new in a series that by this point had got a little too comfortable.
Magnusson is a villain that brought the show to darker, more disturbing places, allowing for the introduction of Culverton Smith and Eurus. Magnusson also forces Sherlock and John to face off against an adversary different to what they are used to.
Mary's true identity also adds an emotional element to His Last Vow that previous series finales had lacked. There is more at stake here than just Sherlock and John surviving and outwitting Moriarty, and this episode wisely balanced its despicable villain and serious tone with some domestic comedy that introduced Sherlock and Mycroft's parents for the first time.
Season three of Sherlock was key to Sherlock growing as a person, and having people to care for and fight for. His Last Vow is a perfect conclusion to an arc where Sherlock has gone from being a better man because of John, to a decent man ready to sacrifice himself, and finally to an actual flawed human we are able to relate to on some level.