Watch Online Movies HD Fmovies. Acid Rain is set in world where a mysterious illness wipes out most of the population, and a dangerous post-apocalyptic world emerges. The film follows the character Jim, who must leave the safety of a compound and navigate his way across the country with what could be humanity's last hope. Along the way, he is faced with the harsh realities of the outside world that has descended into a dark, desolate and dangerous place - But is it already too late for humanity?