The Doctor takes Donna to her first alien planet and they land on a snowy world where they encounter a dying Ood. Soon they find a factory where the Ood are "produced" and sold into the galaxy as servants. Donna can't understand why the Ood don't want to be free but she and the Doctor soon find out that there is more going on in the Ood-Sphere than they are allowed to see. They watch the humans treat the Ood like slaves and some of the Ood get red eyes and turn wild. The situation gets out of control and the humans start to shoot the Ood. Donna and the Doctor are on their list too because they know too much but they still need to find out why the Ood turn against the humans. When they enter hangar 15 they know how the humans could enslave the Ood and help to free them, so they can live in peace on their planet.
I think it's great to have the Ood back in an episode because they are some of my favourite aliens so far. It's interesting that they are all connected to each other and are a peaceful race. This episode shows the darker sides of humanity and I guess it will always be a problem that humans think they are better than others. Maybe we need TV shows to remind us of the fact that we are not better than other humans, animals or aliens. Although this is a more serious episode than the ones before, it still has some funny moments, especially because everybody thinks that Donna and the Doctor are a couple. In this episode we get the first hint that the Doctor doesn't have a lot of time left before this incarnation ends and he doesn't react very good to it. We will see how he proceeds from now on.