A fugitive from justice with a 500 credit reward on his head, Morlock barely manages to escape a crazed group of citizens and the Thought Police. He leaps onto a train in order to escape capture. He ends up in a climate controlled produce car, where, exhausted from the long chase, he falls asleep.

He is awakened by a group of hobos who demand money from the confused Morlock. Not having any, they insist on Morlock's metal foil gloves. When the gloves are removed, all three hobos are infected by a green fungus and become rooted to the freight car floor.

Morlock attempts to escape but is stopped at gun point by the trains's conductor. The anxiety causes Morlock to transform into the hideous Plant Monster and he quickly absorbs the horrified conductor. A pool of brackish slime is all that remains.

His lust for human flesh satisfied, the Plant Monster heads off for the country side and soon regains human form. Exhausted once again, Morlock falls into a deep sleep.

The next morning, Morlock is awakened by the screams of a small child. She is under attack by two plant-like creatures. Morlock manages to free the child from the creatures, but is soon cornered on a cliff edge. He is saved however, by the girl's father, who incinerates the two creatures with a flame thrower.

The girl's father reveals himself to be Bertling, a scientist and an associate of Professor Kroschell, the scientist who created Morlock. Bertling is also trying to create a race of Plant Men, but has failed miserably to date. Bertling is more than happy to offer Morlock shelter for saving his blind daughter, Karen.

Later that evening while Morlock is fast asleep, Bertling discovers that Morlock is a fugitive from justice and the Thought Police are offering a 500 credit reward for his capture. Bertling is torn but decides to turn in Morlock. The 500 credits will pay for the operation to restore his daughter's vision. Bertling wakes Morlock at gunpoint and secures him in an oak shed.

The little girl Karen over hears her father locking Morlock in the shed and tries to free him. As the girl enters the shed, Morlock begins to transform into the Plant Monster. Losing all control, he quickly devours the innocent child and shambles away.

A distraught Bertling soon discovers what has happened and vows to destroy Morlock at any cost.