SPOILERS BEHIND THE CUTS
Exploring what turns out to be a vast Silurian city, The Doctor and the older scientist lady are captured by The Silurians even as Amy and the dad are able to escape from the medical lab. Amy and Dad are quickly recaptured as they try to save The Doctor and the older scientist lady and their lives are threatened as the Silurians make contact with Rory, the older scientist and the mom on the surface.
While all this has been going on, things have been going from bad to worse with the mom having tasered the captured Silurian soldier to death. The Silurian military leader threatens to kill their hostages when Rory refuses to show her THEIR hostage and is about to shoot Amy when the Silurian's political leader shows up, dresses down the military leader and tells her to get lost.
The Doctor immediately tries to set up negotations between the Silurians and the Humans - trade advanced technology in exchange for a place to live on the surface. And it's all going great until Rory and company show up with a dead Silurian hostage and Mom makes a few unenlightened remarks about living in peace with lizardmen that are roughly the equivalent of using the N-word in an insulting manner in Harlem.
Well, there is much running around as The Doctor makes arrangements for everyone human to get back to the TARDIS, the Silurian Leader agrees to put his people back into hibernation for 1000 years in the hopes that mankind will be ready for them then and the poisoned older male scientist is put into hibernation as well, along with the older female scientist, eager to see the world of the future and help ease the transition between the two races.
So it looks like things are okay. Until another Crack in reality opens. The Doctor thinks he sees something in the Crack and tries to reach in and take it. Unfortunately, the leader of the Silurian military chooses this moment to crawl in, declare her desire for revenge and try to kill The Doctor. Rory takes the shot for The Doctor, dies, and is enveloped by energy as The Doctor pulls a screaming Amy back onto the TARDIS.
Despite The Doctor's best efforts, Amy is unable to rememeber her fiancee as the energy from The Crack erases Rory from history. The only sign that he ever existed seems to be the engagement ring Rory left on the TARDIS counsel. And so the episode ends with The Doctor dropping Mom, Dad and Elliot back in 2020, telling them that it is up to them to start preparing people for the Silurian's inevitable return and The Doctor finally examining the object he pulled out of The Crack... which turns out to be a piece of the TARDIS.
THE GOOD PARTS
* The make-up effects on the Silurians are some of the best I've ever seen on Doctor Who.
* The plot is a nice, modernized take on the themes that inspired the original Silurian stories. The key difference is that instead of being a metaphor for the Capitalist cultures of Western Europe and the Communist cultures of the East, this story is a rather effective parable about the evils of racism and how fear and hatred make monsters of us all; a very relevant subject in both the US and the UK right now.
* Amy pick-pockets the guard with her hands cuffed down. Really?
* The Doctor asks Elliot to forgive him for letting him run off alone. While it's nice to see this Doctor admitting that he can make mistakes, I don't think this is something he should have to apologize for... at least not without all the other adults who weren't keeping an eye on the kid apologizing too.
* Those noises the Silurian makes as she is tasered to death? I don't think those are "pain" noises.
* The supporting characters STILL aren't very distinct or interesting and I can't be arsed to remember their names.
* Even the rather loose laws of time that Doctor Who follows are stretched to the breaking point by Rory's death and subsequent removal from time. To wit, he died pushing The Doctor out of the way of an energy blast, which kills Rory and leads - indirectly - to his body being absorbed by the energy from The Crack and erased from time. But if there was no Rory, then The Doctor should have been shot. And yet, he was perfectly fine after Rory was erased. Even if you grant that once a person is erased, a logical paradox can't save them (i.e. if Rory wasn't there to die, he wasn't there to be erased either) The Doctor should have been retroactively wounded.
THE DOCTOR'S DICK MOVE OF THE WEEK
Amazingly enough, he didn't have one.
The closest he comes is telling off Mom for giving into her fear and anger in a profoundly dickish manner. But since she actually deserved it, it's not really all that dickish.
The Final Verdict: A brilliant idea with a strong script heavy in allegory and some amazing visuals is left grounded on the runway by some questionable acting choices, uninteresting supporting characters and ludicrous leaps in logic.