When we last saw the heroes of Doctor Who in "The Impossible Astronaut", River and Rory were exploring the fake TARDIS, and the Doctor and Amy had just found the astronaut of the title. Incidentally, if you've not seen that episode, I recommend that you do so as soon as possible. A quick recap leads nicely into a quick flashback of how they all escaped their respective situations (which seemed rather implausible to me but let's just leave it at that) before they are reunited three months later.
The American locations are once again milked for all they're worth, with rather beautiful shots of Utah in the beginning sequence, as well as a rather obvious CGI shot of the NASA Apollo 11 launch.
The investigation of a monster you don't remember anything about if you look away from it is a fascinating idea for a story, and one which makes me think that Steven Moffat should be writing horror movies in his spare time. The scene that uses this the best takes place in the orphanage with the writing on the wall and the appearance of the Silence within that scene.
This episode definitely sets up more questions than it answers (and for this reason I recommend repeated viewings), from the random appearance of a character from later in the series' run, to the episode's ending, which caused much shock among the dwellers of the Internet. This ending, just so you know, works much better if you go into it with no spoilers, otherwise you're waiting for the moment in question to arrive. Unfortunately, I did not have a chance to see it live, so to speak, and so this twist was spoiled - words cannot describe how annoyed I was.
Once you pass the 30-minute mark, you'll see for yourself that there's no way they can tie up all the questions before next week's unrelated story. And indeed they don't, leaving the Silence to return at some point in the future and giving rise to a phenomenon I am dubbing the "Sparkly Time Child". (Who, if the TARDIS readout is correct, appears to have been fathered by Erwin Schrödinger.)