Wow. I may have had my issues with some of the episodes in this series, but it certainly looks like they've left the best 'til last. And as Paul mentioned briefly yesterday, either everyone involved with Doctor Who has suddenly become much better at keeping secrets, or we've all been completely sucked into believing there's a regeneration in progress when really something altogether different and even more surprising is underway.

The Doctor and Donna arrive on Earth, expecting to find the whole place in uproar. But leafy England is still safe in its early-morning cradle and the milkmen go about their business as if nothing has happened. Because it hasn't, yet. But that soon changes as what feels like an earthquake kicks in. They rush back to the safety of the TARDIS while every science station and alien fighter on the planet stares horrified at their monitors, and regular people walk dazedly out onto the streets and stare stupefied at the sky.

In the TARDIS, all seems calm. Mainly because they're not ON the Earth any more. That is, they're there, but the Earth isn't. And wherever the Earth is, things look an awful lot different. Last week the stars were disappearing and there were fewer heavenly bodies in the night sky to look at. Now, the sky is much fuller than it should be, as Earth is surrounded by planets. Stolen planets. 27 of them in all, including the Earth. The sky looks like something from a Roger Dean painting. No-one on the Stolen Earth can contact the Doctor - all signals have been blocked - and the source of the block soon makes itself known as 200 Dalek spaceships descend, their occupants chanting a single chilling word: "Exterminate."

The massed ranks of military, scientific and Torchwoodish staff clutch each other in terror and go a bit wobbly. Without the Doctor, they're all doomed! Martha climbs into the Indigo device despite Jack's stern warning and, pulling her ripcords, disappears.

Back on the TARDIS the Doctor is running out of ideas. In desperation he decides they have to visit the Shadow Proclamation. After talking his way past the Judoon guard, they learn that the missing Earth is only one of 24 planets to be stolen. 24? Weren't there three more? Yes - Donna remembers Pyrovillia, proving that planets are being stolen from earlier times as well as now. Scratching around for other clues as to what's going on, the Doctor asks Donna to think of any strange happenings. At last! The bees' disappearance is explained. They were jumping ship (well, planet), along some subspace hyperthingy that only bees can follow. Bees, and the Doctor that is. Making a run for it before the Shadow Architect can dragoon them into leading the war, the TARDIS leaves to follow the bees' trail to where the Earth has been moved. It takes them to the Medusa Cascade - somewhere the Doctor hasn't been since he was a kid of 90.

Back on Earth the Daleks are rounding up humans for experimentation and extermination, killing anyone who resists. Grandpa Wilf and Donna's Mum try to stop them with a paint gun, but their efforts are in vain. Nice try though. Even nicer try from Rose, who snuck up from behind (which helped) and used a much more effective gun (which helped even more).

Gathered round their computers, the scattered heroes are surprised when a signal breaks through from Harriet Jones (former Prime Minister). She rapidly configures a network to let them all communicate - Torchwood HQ; Sarah Jane (with Luke and Mr Smith); and one more space - which has to be Rose's...doesn't it? No, poor Rose is left out in the cold. The final slot is Martha's, who's landed in her Mum's hall courtesy of the Indigo device. "Who's she?" wonders Rose, feeling decidedly dejected when she discovers Martha is another companion.

Boosting the power of their combined signals and sending them through every phone on Earth, they place a call to the Doctor. The massive power breaks through the Daleks' jamming technology (or sneaks under it) and the Doctor's phone rings. He and Donna are very pleased to see everyone, including Harriet Jones (former Prime Minister) but still excluding poor Rose, who is getting more frustrated by the minute.

The TARDIS follows the phone signal like a homing beacon and approaches Earth. But the Daleks have tracked the signal to Harriet Jones' (former...oh never mind. You know who she is) house. She hands control to Torchwood just before a Dalek task force breaks in. They know who she is too.

Davros rather rudely muscles in on their call, explaining to the Doctor how he recreated the Daleks "each from a cell of his own body." He's in bad need of some plastic surgery. He also explains how Dalek Caan's emergency temporal shift somehow took him back to the Time War, even though it was time locked, and allowed Davros an escape route at the cost of his mind. Now he sits burbling confusing messages about the future, which no-one pays much attention to. Their mistake, if you ask me, especially as one of his burblings predicts everlasting death for the most faithful companion.

Jack, having fixed his wrist-mounted teleport machine, sets off to join the Doctor, as does Sarah Jane. And then, finally not separated from the group by any malfunctioning electronic wizardry, Rose appears. The Doctor turns, sees her, and they run towards each other for a joyful reunion, just as a lone Dalek rounds a corner and fires off a single shot, catching the Doctor on the shoulder and spinning him to the ground.

The others carry him into the TARDIS, but it's too late. The damage is too severe to repair. There's only one way he can survive, and the regeneration starts.

Well, they say if you're going to tell a lie you should tell a big one, and maybe this applies to other aspects of life too. If you're going to write something that might sound daft, make it SO big and daft that it transcends daftness and turns into something fabulous. And it was. So much action, so much pathos (Rose on the outside looking in! Nooooo!), so many companions, past and present, all working together. And, of course, the supreme leader of the Doctor's ultimate enemy: Davros and an overwhelming force of Daleks. It had everything.

But as a cliffhanger, this has to be the biggest of them all. Why 27 planets? Why Calufrax? Why is Donna the most important woman in all creation? What is the Osterhagen key and why must it not be used under any circumstances? (Translation: it will be used). RTD is a past master at sprinkling tantalising clues throughout a series and pulling them all together in the finale to create something surprising, stunning and exciting. This is his fourth attempt and the stakes are higher, the scale grander and the action altogether more exciting than anything that has gone before.

Of the heaps of speculation there has been about how this will play out, I will say only one thing: I bet none of it comes close.

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