Twelve-year-olds Madeleine, Theo, and Lulu, and thirteen-year-old Garrison, are sent to a remote Massachusetts school to overcome their phobias, but tragedy strikes and the quartet must work together--with no adult assistance--to face their fears.

Magnus and his friends set sail for the farthest borders of Jotunheim and Niflheim in pursuit of Asgard's greatest threat, Loki's demonic ship full of zombies.