This episode amazed me. There is almost no actual Doctor in it, and yet he is. The entire concept takes a bit to wrap your brain around, but once you do, you'll figure out this is one of the best episodes of this series.
It follows Sally Sparrow, who is being watched/ followed by the Weeping Angels, who want the Tardis. They can't move when someone is looking at them. The Doctor and Martha have been taken back to 1969 by them and can only communicate through things left in time by Sally's acquaintances who have also been thrown back into time. The most important of these are the DVDs the Doctor talks to Sally through. This is just a perfect example of television. It shows the other side of the Doctor's adventures. He is just passing through and you don't usually see what happens to the ordinary people, but this time you do, and it's so interesting. The Angels are scary as hell, and it's also cool to note that not only do they stay still when the characters are looking at them, but also when we, the audience, are.
All in all, an extrememely good watch.