In the past, a young fawn named Bambi lives happily with his mother until a poacher kills her. Bambi grows up alone, but meets a doe named Faline, who then gives birth to a fawn. Unfortunately, Faline is fatally run over by a truck carrying toxic waste, and Bambi's offspring disappears. Devastated, Bambi drinks contaminated water from a river, which mutates him into a ravenous creature, determined to get his revenge.
In the present, Xana and her son Benji take a taxi to spend Thanksgiving with Simon and his family—his dementia-stricken mother Mary, his brothers Andrew and Joshua, Andrew's wife Harriet, and their teenage son Harrison—while Simon himself promises to arrive before dinner. On the way, Bambi attacks the taxi and kills the driver while Xana and Benji reach Mary's house.
Meanwhile, three hunters, Michael, Tyler, and Eddie prepare to hunt Bambi. Joshua leaves the house, only to be accidentally shot dead by Tyler. Harrison, brothers Benji and Mary, who start acting strange, know Bambi's name, and has made several drawings of Bambi around the house. Bambi attacks the house and kills Harriet, forcing the family to flee to a caravan. Andrew tries to remove a log blocking the way, but Benji drives off upon seeing Bambi with only Xana and Mary inside; Andrew is unintentionally dragged along with them and dies from blood loss. Harrison encounters Bambi and gets lost in the forest, where he is mauled to death by a group of mutated rabbits.
Xana, Benji, and Mary find Michael, who takes them to a den where they meet Simon and his co-worker Jo. Simon reveals himself as the one who killed Faline and sprayed toxic waste into the river. During the conversation, Benji finds a garage where Tyler and Eddie have caged and mistreated a young fawn. Xana also learns that Simon plans to trap Bambi and kill him, not caring how many lives may be lost along the way. Tyler goes to urinate and ends up being decapitated by Bambi. When Eddie goes to investigate, Bambi rips off his legs and his head.
Benji frees the fawn and runs away; Xana and Simon go after him while Mary encounters Bambi, who tries to kill her. Jo takes her own life to kill Bambi, although he survives. Benji eventually reunites with Xana and Simon, only for Michael to arrive too, threatening them with gunpoint and demands for a fawn. Bambi drags Michael to the forest before approaching Benji. Simon abandons Xana and Benji and tries to flee, but gets killed by the rabbit inside his car. Realizing the fawn is Bambi's offspring, Xana and Benji return it to him. However, a bloodied Michael arrives and fatally shoots Bambi, only to get shot dead by Mary, who has recovered from her dementia. Bambi bleeds out in front of Xana, Benji, and his own offspring.
