In 2011's Rise of the Planet of the Apes an injection of Dr Will Rodman's ALZ-112 temporarily cured his fathers Alzheimers. As a result, the biotechnology company whom employed him, Gen-Sys, developed ALZ-113, a more agrressive version of the drug, capable of being released in vapor form. Unfortunately ALZ-113 proved fatal to most humans, while on contrast increased intelligence in our evolutionary cousins - the apes. The spread of ALZ-113, known as the Simian Flu in the 15 years since its outbreak has devastated the human population worldwide, while conversely giving rise to a new dominant species, a new empire, the Dawn of the Planet of the Apes.