A Fighting Chance

After plague has taken over the world, sibling duo Kailynn and Zavier are fighting to survive. They've seen family and friends slowly die off, all because a sinister disease took over their minds, driving them to insanity. Zavier and Kailynn have some sort of immunity-- and that's something the government is after. They're being chased by drones, military soldiers, not to mention the crazy people in the forest affected by the plague. But when they come across a boy in the forest, nearly dead, Kailynn and Zavier risk all they have to try and help.
Will the mysterious boy be a helpful addition to the team, or will he sabotage them from the inside?

(constructive)criticism welcomed!!!