Moffat's latest episode delivers what was promised - 'Bells' is a contemporary urban thriller given a sci-fi twist, like Skyfall or The Bourne Identity spliced with Time Lord DNA and with a classic Who concept at its core.
The notion of something sinister hiding in the internet could have come off as painfully outdated, but there's nothing hokey about Moffat's 'evil Wi-Fi' - it's a chillingly effective threat, one that calls to mind an old David Tennant episode, and guest star Celia Imrie is wonderfully frosty as chief nemesis Miss Kislet.
With all this talk of chilling / frosty foes, it's up to the Doctor and his newest companion to supply a little warmth - and Matt Smith and Jenna-Louise Coleman bring it in spades. In case you still had any lingering doubts after Christmas special 'The Snowmen' - and I'm not sure why you would - the pair are absolute dynamite here.
It's quite a task to strike up an exciting, sparky chemistry with another actor without sharing a single scene, but Coleman's surprise Doctor Who debut in 'Asylum of the Daleks' proved how well she and Smith could work together.
Reunited / meeting for the first time, the Doctor and 21st Century Clara banter and bicker wonderfully - the Hepburn / Tracy inspiration is obvious - with Smith and Coleman rapid-firing Moffat's sizzling dialogue.
There's elements of both Oswin and Victorian Clara to the updated model, but Jenna-Louise Coleman is, if anything, more endearing than ever here. She may be at the centre of a baffling conundrum, but Clara is far more relatable than either her 19th century counterpart or the super-sassy Oswin - there's a running gag involving a cup of tea which I particularly loved.
Matt Smith - now a seasoned Doctor Who veteran - also continues to impress, 35 episodes in. Each and every Who episode is an opportunity to lure in new viewers, but that's even more true of a series opener - and Steven Moffat knows this, so 'Bells' is a terrific showcase for the show's lead.
Mischievous imp, action hero, dark enigma - Smith gets a chance to play it all across this episode's jam-packed 42 minutes and, with no Rory substitute in place, there's also a fun frisson between the Doctor and his companion that we've not seen for a while. Traditionalists can cool their boots though - it's mostly one-sided and the Doctor is still *terrible* at flirting.
All involved with 'The Bells of Saint John' should be very proud. Doctor Who's first outing this year is an electrifying comeback for a show that was already in fine form - a shot of adrenaline to both hearts.
Doctor Who: The Bells of Saint John airs on Saturday, March 30 at 6.10pm on BBC One.