The Doctor and Donna arrive in the middle of Frozen. Later on, we really do get a sing-along, but for now, let's just be happy that we have more Ood.
Except we're on the Ood Planet (close to the Sense Sphere-HAI SENSORITES HAIII). Where we have a industry. To sell Oods as slaves.
Apparently the "red-eye" thing is happening again, this time without any eldritch interference. These Ood are called "rabid Ood", and get very violent. Donna feels bad for them, while the Doctor is deeply skeptical that a servant race could just evolve. They discover a "herd" of Ood that haven't yet been prepared for servitude, and there's the answer. Ood don't normally walk around with orbs in their hands.
Normally they walk around with their hind brains in their hands.
Thanks. Thanks but we have to go THANKS.
So, basically, they're being lobotomized. The intact Ood sing, and it's very pretty and everyone cries a lot. Then the Ood prepare for VIOLENT REVOLUTION! Halpen, the CEO, runs for a warehouse, and the Doctor and Donna follow.
The warehouse has a giant brain in it. The Ood, it seems, have a collective consciousness. The brain is already being impeded, but Halpen decides to destroy the brain altogether. Luckily, there's an abolitionist in the company, who has actually lowered the force field around the brain. Then it's also revealed that Halpen's servant Ood has been dosing his tea with...something...that converts Halpen into an Ood, and yes, the visual is just as disgusting as you would expect.
The Ood are freed to sing their song, which will include Doctor-Donna, which is the most plot important grammatical error EVER.
I loved getting another look at the Ood, and the fact that Donna will snap right back at the Doctor when he gets in one of his "inferior human" jabs. (I've come to accept the Doctor's occasional self-righteousness; it gives him that intensity that Tennant does so well.)
The Sontaran Strategem
Here we have a rare instance of the Doctor actually answering his phone (which his answers less than I do mine). Martha has called him on behalf of UNIT: shenanigans are ensuing on Earth! The Doctor and Donna tag along on a raid of the ATMOS factory, ATMOS is a GPS made by Luke Rattigan, the infernal lovechild of Wesley and Adric, and UNIT suspects wacky alien hijinks are ensuing, what with the systems going haywire and murdering the car drivers.
And they would be right, because they have clearly seen the title of this episode! General Staal is not only using humans' love of shiny new technology against them, but also making naked clones of Freeman Ageyman to distract them.
They used this visual A LOT in the trailers. A whole lot.
Donna decides to go back home briefly to warn her family, and the Doctor wastes a whole eloquent goodbye speech on it. In fact, the Doctor has a lot of epic speeches that he uses at inappropriate times, come to think of it. (That bunny will never be the same.)
It all ends when Wilfred is tragically trapped inside a car emitting poison gas, just as all the other cars emit poison gas.
And if you made it through that last sentence without giggling, congratulations, you are no longer in middle school.
Great cliffhanger, annoying reactions to people with GUNS of all things. (At least Martha points out the nonsense of this attitude.)
The Poison Sky
Donna's mother saves her grandfather via axe, and the Doctor warns UNIT not to fight the Sontarans, because they will get their asses handed to them. This doesn't matter, because the closest thing we have to the Brig (who is still in Peru) is all out of bubble gum, and kills the Sontaran second-in-command, because we all got a little tired of the Doctor making fun of UNIT without a Brig to counteract him.
Also, the Doctor has to make an Empty Child joke.
Meanwhile, Not!Martha has given the Sontarans control over UNIT.
The Doctor figures out that the Sontarans are trying to convert the atmosphere to something they can breathe, but humans can't, because Sontarans don't like to share. After rescuing Real!Martha, they arrive at the academy to find Luke having a realization that he is not, in fact, a special snowflake. While he has teenage angst, the Doctor actually does something useful and builds a devicey thing that will burn off the poison while leaving our atmosphere intact, because science. But Luke has decided if he can't be cool at one thing, he can be cool at another thing, and is the one to set the device off, exploding himself and the Sontarans.
Martha goes to the TARDIS to say goodbye, but Sexy is feeling trolltastic, and transports all three of them while the Doctor's severed hand in a jar bubbles with foreshadowing.
It was a fun little two parter, and it was nice to see Martha again and see how capable she has become.