Equestria has become overpopulated. Scientists predict that, given the current rate of expansion, they only have ten years before their dwindling resources finally run out, and the planet is rendered inhospitable to life. In a desperate attempt to save her people, Princess Celestia authorizes Operation Gateway. Top scientists and magic users from around the world attempt to create a portal to a new world, where they hope to settle in peace.

Meanwhile, Earth has already passed its breaking point. Most of the surface is incapable of sustaining life. It is only thanks to a rigid system of recycling and a totalitarianism government that a small population of one million humans and a few hundred cattle manage to survive in the city of Last Hope. It is a delicate balance, and any attempt to disrupt it is harshly punished.

When Operation Gateway lands the pony's vanguard right in the middle of Last Stand, Earth's last humans are divided. Some want to help the ponies, sympathizing with them, and hoping that, with their help, they could revive their dead planet. Most see them as a threat to their survival, and desire only to take what they can from them before killing them off.

Victus is one of the later. As one the Sewer Rats, he has learned how to survive outside, and he knows that humans and ponies cannot both survive on the dead planet he calls home. But when a rainbow-colored Pegasus risks her life to save him, he is forced to decide whether he should side with the ponies that care for him, or the government that promises him wealth beyond his imagination in exchange for the answer to a question that could mean certain death to ponies in both their worlds.