The Third Day, the Frost — John Marsden

Book 3 of the Tomorrow series

What's the biggest danger you can think of? This is bigger.

What's the toughest challenge you can imagine? This is tougher.

What's the greatest fear you have? You're about to find out.

“How long do you think they'll keep looking for us?” I asked Lee, as we lay there.

“Until they find us,” he answered grimly.

They came in summer. They fell upon the land swiftly and suddenly. Through autumn they spread, like locusts, like mice, like a plague. Now it's winter. They're still here. But so too are Ellie and Homer and their friends.