Much of that has to do with the crisp dialogue, the intelligent writing and the leads. Jonny Lee Miller displays sufficient arrogance in his awkward posture and twitching to capture the essence of Conan Doyle's great detective without being idiosyncratic or annoying. This season his manner has also softened enough to maintain Holmes' self-confidence but allow for moments of humility that make the anti-social and emotionally suppressed character someone we can sympathize with.
Watson, meanwhile, honors Conan Doyle's intent as an intelligent, dedicated friend and the writers never pitch Liu as anything less than an equal partner in the team. As exasperating as Holmes is, especially coming out of the relapse he suffered in Season Three, Watson's support of him never feels forced and the acting and writing ensure there is no need to resort to a degree of attraction to justify their close relationship.
This season also has a recurring role for John Noble as Sherlock's estranged father, Morland. Noble can be equally charming and chilling, which makes him ideally suited to the role of a global mover-and-shaker with fluid ethics. Sherlock's investigation of a past attempt on Morland's life provides a reason for them to interact and the sparkling exchanges between Miller and Noble are standout moments in every episode in which they occur. Thankfully, this subplot intermittently surfaces throughout the season and only towards the end is it revealed whether Morland puts more value on his fortune or his family.
It's true that Elementary's fourth season doesn't stray far from the basic procedural format. Nevertheless, it's a case of intelligence triumphing over formula. Combined with plenty of wit and playful nods to the source material (there is a version of The Hound of the Baskervilles this season, for instance), this ensures that Elementary continues to be more than just a series of mundane murder mysteries