Plant pals Nate and Patrice suggest a brilliant idea: thwart any attack from the zombies by putting defending plants named 'Guard-ens' inside homes, as well as in yards! But as soon as Mr. Stubbins informs zombie leader and Pop Smarts lover Dr. Zomboss, he quickly becomes obsessed with circumventing this idea with an epically evil one of his own - building cages disguised as homes to trap all the tasty brains (and the people they reside within) before the Guard-ens can get there. The plants, Nate, Patrice, and Crazy Dave must now counter Dr. Zomboss's havoc-filled scheme!