SPOILER ALERT: This weekly blog is for those who have been watching the new series of Doctor Who. Don't read ahead if you haven't seen episode one – The Impossible Astronaut

"This is cold. Even by your standards, this is cold."

Hello sweeties! And welcome back. There's really nowhere else to begin than with that death scene. Sudden and brutal and unexpected even though, on thinking about it for even a minute, it was really quite obvious who was going to die. But the cremation on the boat and Amy's numb horror ramps things up to a series-finale level of intensity from the off – and it doesn't let up for the duration of this staggeringly confident series opener. There's little time to even breathe as the episode then switches into an Oval Office comedy of manners, morphs into gothic horror and finally flings you to the ground with its cinematic cliffhanger.

Steven Moffat has thrown away the rule book and made Doctor Who as, you imagine, he's pictured it should be his whole life. Killing the Doctor leaves the shape of the series mapped out, raises the bar so that no one is safe, and sees Amy, Rory and River facing a terrible dilemma.

The US setting is expertly judged, using all the right iconography to spell out a great American adventure, the plains of Utah, the Oval Office and NASA, and our eccentric British foursome bumbling through it. Look everyone: Doctor Who just raised its game.

"These are my special operatives; The Legs, The Nose, and Mrs Robinson"

The other remarkable thing about The Doctor's death is that it changes the dynamic – by giving Amy, Rory and River a secret from the Doctor, their roles become that much more crucial. In a flash, Doctor Who is now an ensemble show, with a weird little family and tangled web of relationships at its heart.

The tragic backwards love story of River Song just gets more and more genius with every appearance. Each time, we see more depth and vulnerability – when she finally opens up to Rory while picking the lock I found myself with real tears in my eyes. And yet Alex Kingston's delivery just gets camper and camper, helped along by lines like: "Don't worry, I'm quite the screamer!" You can't imagine that any other actor is having quite as much fun as she is right now.

Everyone seems to be much better in their roles than last year, with Smith's Doctor off the scale; the tense face-off with River, and the hesitant smile that cracks across his face when Amy swears on fish fingers and custard were both quite extraordinary.

Fear factor

The Silence, then. Horrific to look at, and they're a standard Moffat psychological trick, but the most refined to date. Monsters that you forget as soon as you can't see them fit neatly onto a credible list of things that really could be there in the corner of your eye. So just how long have they been there? That reveal scene of Amy and the old lady in the toilet was pure David Lynch.

Mysteries and questions

We've met the Silence now, but there are still mysteries to be unpicked. What's this about how Silence will fall? And what is it that they want? That underground maze room is the unexplained Tardis that popped up in last year's story The Lodger, which was surely a seed for this whole series. Amy Pond pregnant? Who is the little girl? What is the astronaut? And what do either of them want with The Doctor? .

Time-space debris

• Shrewd casting alert: Mark Sheppard is US sci-fi royalty, having appeared in Star Trek Voyager, Firefly, Dollhouse, Medium and Battlestar Galactica.

• "That's OK, you were my second choice for President, Mr Nixon." And right away, you know Canton Everett Delaware III is going to be one of the good guys.

• There's a tradition forming of family members playing different versions of the cast. After Karen's cousin Caitlin Blackwood played young Amelia last year, the older Canton on the beach is actually Mark Sheppard's dad, William Morgan Sheppard.

• "Three of America's founding fathers. Lovely fellas, two of them fancied me." Ah yes. The return of bigoted panic over the "gay agenda" cannot be far away.

• The early Nixon, before most of the bad stuff, is presented as something of a hapless good guy.

• "I live for the days when I see him, but I know that every time I do, he'll be one step further away." River lets the mask slip in an unlikely pairing.

Next week!

The Doctor's imprisoned in Area 51 and America is occupied. How the blazes are they going to get out of this one? Your thoughts, please.