It isn't always easy being the smartest guy in the room. There's a lot of pressure that comes with celebrated genius, and if you can't demonstrate it each and every time out, people can start to look for a smarter person to take your place.

Nor is it all that easy to write the adventures of the smartest guy in the room — particularly if, as Steven Moffat and Mark Gatiss have done with "Sherlock," you insist on only making three 90-minute episodes a season. These modern-day adventures of Holmes (Benedict Cumberbatch) and Dr. Watson (Martin Freeman) are beloved, but the series doesn't have the leeway a more traditionally-structured series — like, say, CBS' own modern-day Sherlock series "Elementary," which does 22 episodes a season — get. The scarcity of "Sherlock" makes every episode an event, which is a lot to live up to. Yet for the most part (the second episodes tend to be less impressive than the first and third), Moffat and Gatiss pulled it off through the first two seasons. Their take on these familiar characters and mysteries have been exactly as smart as their dark and mysterious hero, and they've become a sensation in the UK.

They've also made a star of Cumberbatch, and both he and Freeman have been so busy making movies (including teaming up on"The Hobbit") that tonight's third season premiere (10 p.m., PBS) will be the first new episode in nearly two years(*), and following up on the season 2 cliffhanger where Holmes appeared to fall to his death from a rooftop, but was revealed to still be alive in the final frame.

(*) The entire third season has already aired in the UK, and the usual blog spoiler rules apply: if it hasn't aired in America yet, it's a spoiler. I'll have another post in a few weeks so we can discuss these episodes in detail; for now, I want all English viewers and/or torrenters to be as vague as possible.

So "Sherlock" fans have had two years to concoct theories of Holmes' survival, and to build up the show's return into an even grander event than usual. That is perhaps more pressure than any television show can bear, and the Gatiss-penned premiere, "The Empty Hearse," crumbles under that pressure. Gatiss is a very clever man (and plays Holmes' even more brilliant brother Mycroft on the show), and you can see him tying himself up in knots trying to come up with a solution to the cliffhanger that won't underwhelm after all this time and all this speculation, even as he's commenting on the fan response. (The episode features so much meta commentary and so many winks to the audience, you half wonder if Gatiss flew Dan Harmon from "Community" in to punch up the script.) It's a mess, even with the pleasure of having Cumberbatch and Freeman together again.

The season settles in after that (or, as much as a three-episode season can). The second episode deals with the unique qualities of the Holmes/Watson friendship while telling a series of interlocking smaller mystery stories (in that way, it evokes the first season finale), while the Moffat-written third pits Holmes and Watson against a media magnate who, like Holmes, understands that knowledge is power, but who uses his power for much crueler purposes. It's the most straightforward of the season's three adventures, and perhaps not coincidentally, the best.

When you're smart men writing about the smartest man of all, you may feel the need to demonstrate your smarts in every possible way, with every beat of the story. But Holmes and Watson are such enduring characters, and these versions written and played so well, that they don't always require such elaborate mental gymnastics.

Alan Sepinwall may be reached at sepinwall@hitfix.com