SEVENTEEN-YEAR-OLD Mary Katherine (voiced by Amanda Seyfried), who prefers MK for short, reluctantly heads out of the city to stay with her madcap father, Professor Bomba (Jason Sudeikis).

Since the death of his wife, Bomba has thrown himself into his study of tiny ecowarriors called Leaf Men, who are invisible to humans and apparently reside in nearby trees and brooks.

Naturally, MK thinks her father has lost his grip on sanity until she is magically shrunk into this fantastical realm of valiant warriors and talking flora.

MK is taken under the wing of Leaf Men rebel Nod (Josh Hutcherson), whose gung-ho actions disappoint his commanding officer, General Ronin (Colin Farrell).

When a rival army of evil-doers called Boggans led by evil Mandrake (Christoph Waltz) attempts to take over the forest and destroy the Leaf Men and their benevolent leader, Queen Tara (Beyonce Knowles), Nod and MK stand side by side against the onslaught.