Last night, David saw a spaceship crash in the woods! But no one seems to believe him. The next day, his father investigates the site--and returns, acting very strangely. Next it's his mother's turn, then his teacher, then a classmate--all programmed, zombie-like, with strange scratches on their necks. David's last chance is to get to the Marine base and alert them--before a vital secret mission is sabotaged, before the Martians take over the planet Earth!