Yes, but I don't want a stray eye to see it.
I urge you to watch it yourself because it really is great. You only get one chance to be surprised.
There is a virus that came to earth, presumably from a meteorite that crashed into the swamp, that was able to survive in the climate of Hinamizawa. Whenever someone from the town would leave, the virus would be put under stress and would attack it's host. Additionally, extreme stress would "set-off" the virus as well.
The benevolent spirit that watches over the town, Hanyuu, has been bringing Rika back in time as best she can to hope that eventually everything turns out correctly. Rika has no idea why the tragedy occurs, or who's causing it. And each time she only has days to try to arrange things to work out. It's Groundhog Day with death.
When their true rival, Takano, is discovered, it becomes a battle of wills. The will of Takano against the will of their club.
That's the meat of it. Anything specific you wanted to know? They explain pretty much everything.