Benedict Cumberbatch in 'Sherlock' series two finale 'The Reichenbach Fall'
PBS Benedict Cumberbatch in 'Sherlock' series two finale 'The Reichenbach Fall'

Who is the greatest on-screen incarnation of Sherlock Holmes? It's a complicated question -- acting can be difficult enough to quantify even without the challenge of taking on the most frequently portrayed fictional character in the history of film and television. Each Holmes has had to compete with and be compared to the ones before him, going back to the anonymous actor who starred in the first Holmes film in 1900, a silent 30-second short from Arthur Marvin.

Of the dozens of actors to take on the role in the over a century since, a few have been truly outstanding, like Basil Rathbone, to whom the highly entertaining cycle of Holmes films in the 1930s and '40s owe nearly everything. Jeremy Brett's portrayal of the character on British TV starting in 1984 is widely considered definitive -- Brett researched the canonical Holmes meticulously to that end. So I don't mean it as a slight to either Rathbone or Brett or anyone else who's played the iconic detective when I say that the greatest performance as Sherlock Holmes is in fact that of Benedict Cumberbatch, star of the BBC's "Sherlock," the second series finale of which aired here in the United States last night.

Sherlock 2

Cumberbatch benefits greatly from the approach taken by "Sherlock" creators Steven Moffat and Mark Gatiss, Holmes fans who aimed to free the character from what they felt was a paralyzing traditionalism in adaptations. By setting the show in present-day London, they've found a way of getting at who Holmes is as a character, giving everyone from the writers to the designers to the actor playing the role the opportunity to focus on who Holmes is, rather than who he has been. While the idea is a fine one, without an adept and delicate execution the whole enterprise would come across as a self-consciously clever literary trick, a game of “how many Holmes references can we fit in one episode,” or, worse, a cynical concession to modern audiences' disinterest in history and literature.

Fortunately, Moffat and Gatiss' "Sherlock" is carried off with remarkable skill, with every creative level of the show combining holistically to create a vivid portrait of Sherlock Holmes as a fully developed person, and not just a bundle of costume choices and famous phrases. Not to downplay the excellence of Cumberbatch's work, but great performances don't exist on an island. "Sherlock" is constructed so that the audience sees what Holmes sees, with creative use of camerawork, editing and computer-generated effects. Even establishing shots are selectively blurred to pull focus to one particular area of the shot, as a nod to Holmes' powers of observation.

As for Cumberbatch's performance, his physicality is a delight -- he alternates between furious activity and catatonic stillness, seeming to be in motion even when still and to exist in a series of meticulously constructed tableaux when in motion. His Holmes is introduced to Martin Freeman's Watson as a potential flatmate, and proceeds to do an eerily accurate (and signaturely Holmesian) job of sizing Watson up based on a handful of physical details, with the ironic capper of mistaking “Harry” for Watson's brother, when in fact it's short for Harriet. Cumberbatch's Holmes explodes forth with extremely rapid bursts of text when itemizing his observations, his tone an exquisite mix of rigorously academic precision, dry wit, and an almost sensual pleasure in the befuddled awe on the faces of his audiences.

Cumberbatch balances Holmes' investigative genius and his social illiteracy with casual perfection.

Over the course of the first three-episodes series, we saw many displays of Holmes' practically supernatural deductive reasoning, as well as his near-complete inability to deal with any other aspect of reality other than his work. Cumberbatch balances Holmes' investigative genius and his social illiteracy with casual perfection. The fact that he manages to charm and compel in the same beat as he exasperates -- as when he crashes Watson's date with Sarah (Zoe Telford) -- and that it feels inevitable that he does so, is a measure of his performance's quality.

His chemistry with Freeman is also noteworthy; with the latter giving a true supporting performance as well as the odd timely reminder to Holmes that there are other people in the world, people whose value extends beyond being an audience for the detective's brilliance.

The way Cumberbatch handles these reminders is one of Sherlock's better running jokes, as he always has some tiny pause or facial twitch to indicate that the moment has registered. And he does learn from these reminders, building to a beautiful blip of a moment in last night's episode, “The Reichenbach Fall”: after Holmes is arrested, Watson gets himself arrested as well as a sign of solidarity, and for the briefest moment, the corner of Cumberbatch's mouth twitches. It's a subtle gesture that revealed that, for all Holmes' belittling Watson's intellect and personal life, he genuinely loves his friend -- and all in the blink of an eye.