It's raining red acid on Under the Dome Season 2 Episode 3. The townspeople initially believe it's raining blood, but Rebecca quickly determines it's acid instead. It burns the skin something terrible.
A conflict between religion and science is raised over the red rain. Is it a sign of the coming rapture? Or is it from a build up of algae in the lake? Given the different thoughts, it could actually be a sign of both. Weird, right?
Several outstanding questions are answered at least in part over the hour, but they raise even more questions for the residents of Chester's Mill.