Following the extermination, Emry has the whole of Earth to himself. No one is left to fight, and nothing is left to fight for. The whole world is literally at his feet.
As is a paper plane...that he didn't throw.
Earth is losing in a war against an alien race that has no mercy for human kind, but when one man comes close to finding a way to turn the tides of war his memory from his teenage years to now is wiped clean.