The Doctor and Donna encounter the Ood on the planet they’re sold from. Again their eyes go red and they’re murderous – is the Devil back or is something else going on? We’re repeatedly told that the Ood are born to be servile, but as their rabid madness escalates, we find that presumption to be a lie expounded for profit. They may be servile, but that state has been created – by Tim McInnerny’s corporation.
A grittier episode, with a morality tale against human trafficking and slavery built in, this is a nicely timed third episode. The Doctor’s reminder to Donna that her mass produced clothes are created by modern day slave labour. “I can’t tell what’s right and what’s wrong anymore,” says Donna, and she’s right. The Doctor’s abilities are again shown as a dual-edged sword – last week we find him able to see the potentiality of all actions, yet trapped by their fixedness; this week we see his telepathic ability, but he’s assaulted by the pain of the Ood’s song of captivity. It’s a chance to get to know the Tenth Doctor much more deeply than just through his responses to the Time War. Is he running out of time?
There are serious undertones of 28 Days Later – man’s messing with the natural order of things leading to a terrible outcome for everyone, particularly the most vulnerable. A pretty socialist, quite radical episode if you think about it – the Doctor rebelling against corporate humanity for the good of honest alien-kind. It was one of many hallmarks of an excellent episode.
Another hallmark of course was this:
“I think your song must end soon.”
Really? That’s another strand to take into account. We don’t have ‘Bad Wolf’, we have a much bigger arc opening up. Could this mean the Doctor-free episode where the assistants team up to save him and presumably time itself? Or could it be something bigger? Something which started before 1:1 in 2005? How much of what we think we know about the backstory between Classic and New Who do we know? Is Donna what she seems? Is Rose what she seems? I’ve wondered for some time whether Rose was manipulated into killing the Daleks – if so, who by?
Cosmodaddy 
I agree, the episode was fantastic on many levels. On the surface it was an enjoyable and often exciting adventure and on a deeper level there was a strong social and cultural message. I really like Donna as a character and as an assistant as she challenges the Doctor, makes him explain himself which is something Martha never did and Rose was an expert at. I like conflict between the emotional human mind and the Doctor’s rational view of the ‘big picture’. This is something we lost for a whole season.