The Doctor, River and her team are chased through the library by the shadows and they don't know if they will be able to escape them. One after the other becomes the victim of an attack of the Vashta Nerada. Meanwhile, Donna is trapped in a virtual world and can't remember the Doctor. There she has a husband and children but something about this world is strange. When she talks to the ghost of Miss Evangelista, she sees that nothing is real but she doesn't want to give up her family. The Doctor has discovered how the Vashta Nerada came into the library and he can't believe that he hasn't thought of it before. When he and the others reach the data core of the library, he is a bit shocked to see that it's the conciousness of a little girl that controls everything. The self-destruction is turned on suddenly and nobody can turn it off. Will the Doctor find a solution to save everybody?
The Vashta Nerada are a great enemy for the Doctor and he really needs some time to find out how they came into the library. I like that he still tries to talk to them even though they kill everyone in mere seconds when they can reach them. He is just not someone who can kill easily and I think that's a good character trait. The story line with Donna is interesting as well. She somehow knows that something is wrong but she doesn't want to believe it because she is happy with her family and doesn't want to loose them. You somehow knew that the little girl had something to do with the library but I wouldn't have thought that she controlled it or that it is her home. The scene between the Doctor and River is so heartbreaking although he doesn't know her yet, there is this connection and I'm glad that he was able to save her in the end. I think this episode brings the story to a good end.