Once upon a time, a fenced-in village existed in the middle of a Forest infested by the Unconsecrated (i.e. flesh-gobbling zombies). Enter Mary. She's minding her own business, washing her clothes in the stream, when her childhood pal Harry pays her a visit. And pops the question—yup, that question.
Before Mary can answer, the village sirens start a-wailing, which is code for… zombies in the house. Save yourselves, people. Mary hightails it for the village, knowing full well as she hustles along that this siren went off because she dilly-dallied at the stream. See, her mom really wants to find her newly zombified hubby, and Mary knows that because she stayed away too long her mom probably got too close to the fence while looking for him and is now infected herself. Bummer.
After Mary's mom joins the ranks of the moany-groanies, Mary's brother Jed kicks her out of their house (as a Guardian, he's not keen on having to chop off his mom's head if he sees her in the Forest). So Mary joins the Sisterhood, led by the power-hungry Sister Tabitha. Sister T can see that Mary isn't super happy about becoming a God-fearing nun for life, so she threatens to sic the Forest of zombies on her if she refuses to toe the line and act like she likes it.
While cooped up in the Cathedral, Mary finds out her other childhood pal, Travis, has a ridiculously bad leg injury and the Sisters are taking care of him. Mary visits him every day and "prays" with him… which means she actually just tells him stories about the ocean. Dreaming of the beach together means true love for Mary and the Travster, which is too bad since he's Harry's brother and engaged to Mary's bestie, Cass. Drama.
Harry asks for Mary's hand again, and she says yes. Insofar as this means she can escape the Sisterhood, this is a pretty awesome development; but insofar as she's in love with Harry's brother, it's pretty lame.
In the meantime, Mary notices that a girl in a bright red vest entered the village from Outside and is locked in a room in the Cathedral. She finds out her name is Gabrielle and is eager to learn more about her and where she's from.
Mary and Travis run into each other at the Hill and have a nice make-out session. Mary asks Travis to come for her and whisk her away from Harry, but before he can answer, they catch a glimpse of Gabrielle, who is now a super-zombie and totally freaky. So much for getting to know her.
Fast forward to the morning of the wedding (PS: Travis never came for Mary). Instead of waking up to church bells, the village wakes up to the screaming of the sirens. Turns out super-zombie Gabby and the zombie horde are attacking the village.
Harry and Mary escape by the skin of their teeth onto one of the fenced paths into the Forest. They're joined by Travis and Cass, Jed and Beth, a little boy named Jacob, and Mary's new pooch, Argos. See ya, village, wouldn't wanna be ya.
The gang wanders down the path for a while before stumbling upon another village. Mary knows it was Gabrielle's village, though it's also been overrun by zombies. While the rest of the gang escapes into the tree house part of the village (zombies aside, Shmoop wants to go there), Mary and Travis end up stuck in a big ol' house together. Alone. Ah, shucks.
At first it feels like heaven on earth, but then Mary stumbles onto some old photos and dresses and becomes super obsessed with escaping the village. Luckily for her, some zombies finally break down the house door, forcing her and the Travster to get outta there. Thanks to Argos and his furry jaws of death, Mary shoves Travis into the attic and swims through a sea of zombies unscathed.
The tireless threesome crosses the divide into the tree house village with a sheet-rope, a barrel, and some serious climbing skillz from the Travster (who still almost gets chomped to death by the zombie horde).
Mary and Travis have a heart-to-heart, and Mary realizes that she needs more than the Travster to be happy. She just can't quit thinking about her ocean. The others agree to head back to the forest paths once the weather cools down.
You know that phrase about how the best laid plans are meant to be broken? Jacob accidentally starts a fire and burns down the village, so it's go time—so much for waiting for the weather to cool down. Travis saves the day by running the rope through Zombieville to the gates, though he also gets himself bitten in the process. Mary slides down the rope to help him, but he's already on his way to becoming a zombie. Before Mary slices off his head, he tells her that he'd already been bitten back at the big house, so he was a dead man either way.
The gang is back to wandering through the Forest, and by this point everyone's depressed and starving. They come to the end of the path, and Beth about has a hissy-fit.
Mary leaves everyone in the dust and scoots into the Forest to find the ocean. The Unconsecrated dogpile her, and she'd be dead, except that Jed saves her life. Yep—he decided to help her follow her dream. Unfortunately for him though, he slips off a cliff and dies.
Mary tries to find his body in a raging river, but falls in and ends up gasping for air on a beach. Turns out the ocean is at the end of the river (funny how that works). A man comes along and almost cuts off her head, but she proves she's alive and they end up walking hand-in-hand back to his lighthouse. The end.