Earth was invaded. Earth was conquered. And humanity was summarily subjugated, as 400,000,000 people were culled. The terrifying part was this only took the Peacekeepers a second. There wasn’t even a chance for us to fight back. So, in the blink of an eye, questions like whether or not we’re alone in the universe or if we’re at the top of the food chain were answered. We were not. Not by a long shot. Despite the mass murder, the Peacekeepers promise they’re benevolent. They don’t want to rule Earth. They don’t want to control humanity. They just want us to stop playing around with AI and genetics. Willing or unwilling, Morgan and the rest of humanity are now members of the Collective. And like every species in the Collective, they have to learn to play the Game. So, what do you do, when an AI offers you the opportunity to play the greatest tower defence game the universe has ever created? You accept, of course. Learning the rules and finding a way to survive can come later. Morgan certainly thinks so. But when aliens are attacking your station, and giant, six-eyed rats are eating your robotic face, you start to have your doubts. Accidently starting a war doesn’t help, either. But what are you going to do? You’re the first line of defence—and you’ve got a job to do.

Morgan Mars is doing everything he can to protect humanity from alien invasion, but even his new organisation, The First Line of Defence, isn’t enough to save what’s already lost. Sectors are collapsing like dominoes as the aftermath of the 20th Cycle invasion leaves everyone trapped in the falling Sectors. No one knows what to do. No one, that is, except Nicholas Thistlebush. He has a plan to save Sector 6.The only question is, what will it cost him?