Applejack's parents drop by Sweet Apple Acres for the Apples' next family reunion, as the entire family is overjoyed that they returned. However, the reunion is ruined when all the crops in the farm die. With culprits being ruled out since the mass destruction of the plant life and agriculture around them. King Aspen and his kingdom have come claiming that Thicket is dying, and so is the Tree of Harmony, which slowly dries out the Elements' power. After a long journey with the Lodgers, the reason is discovered by the Alicorn of Life that something is sapping required nutrients from the world, and even the Guardians of Harmony are affected. The culprit is at first revealed to be Well-To-Do, but it's later revealed that he has become the assimilated avatar of a magic plant monster he accidentally awoken during his work on Eveefree Forest. This monster is called a Treant, a much more feral ancestral creature to ents that are powerful but have the intelligence of Neanderthals. Collecting the rest of it's eon-hibernating kind, they seek to destroy modern society with overgrowing vegetation to restore the dying world. They also find their creator, Princess Thrivia, the Alicorn goddess of grain, agriculture, harvest, growth, and nourishment, who had created the Treants as guardians of her home, family and the care of life until the Chaos War turned them into ravenous near-immortal monsters obsessed with drying out nutrients in the world to destroy urban society built above nature and she had to put them into eternal hibernation which was locked by trees in what is now the Everfree Forest. When Well-To-Do tore these trees down, it almost released them until recently the last lock tree died out. Now the leader Treant, dubbed Hatewood for his particularly angry nature, has possessed Well-To-Do and turned him into a half-plant half-Minotaur abomination that has to be stopped.