Dr. Zomboss invents a Cold Crystal, which is capable of freezing Neighborville, creating an eternal winter and burying both plants and humans in snow and ice! With most of the benevolent, zombie-battling plants chilled and immobile, Zomboss hopes to lead his cold-blooded zombie troops on a mission to overrun the city. It's up to Nate, Patrice, Crazy Dave, and the fieriest plants to adapt, fight on, and save Neighborville - with the help of pirates!