Three sorority sisters Mary (Rachel Melvin), Jenn (Lexi Atkins) and Zoe (Cortney Palm) were planning on spending a weekend at Mary's cousin's cabin by the lake with their respective boyfriends Tommy (Jake Weary), Sam (Hutch Dano) and Buck (Peter Gilroy). But when Jenn learns about Sam's infidelity and dumps him, Mary decides the three girls should go to the cabin without the boys, much to Zoe's dismay.
The calm and uneventful first day at the cabin takes an unexpected turn when the three boys join the girls uninvited, and later so does a strange-looking aggressive beaver with glowing eyes, the first of many...
This film contains examples of:
- Aborted Arc: The plot point of Sam's infidelity gets put on hold towards the end of the movie and never actually concludes, on account of all of the involved parties dying.
- An Arm and a Leg: A zombie beaver chews off Buck's foot.
- Asshole Victim: For killing Zoe's dog and having an affair with Mary, Sam got what he deserved when a zombified Jenn bites off his penis and he gets killed as a zombie by Mary.
- Attack of the Killer Whatever: Beavers in this case.
- Bad People Abuse Animals: Although a necessary evil since it allowed everyone to escape, Sam sacrificing Zoe's dog so they can escape the lake is just another example of how much of an asshole he is. Especially since he had a previous scene discussing his affair with Mary.
- Book Ends: The same careless truckers appear in the first scene and the last scene. In the first scene, they run over a deer, accidentally dumping the chemicals into the lake. In the final scene they run over the Final Girl.
- Decoy Protagonist: Jenn, as it turns out, she hits a lot of points for being a protagonist at first (her emotional problems are presented as a major plot point, she appears to be the most careful and savvy of the six characters, she does not have sex during the movie while everyone else does, and she has an encounter with a beaver alone while isolated from the group). And then she turns into a beaver-zombie.
- Dirty Old Man: Both neighbors, while aging, are shown to be well-versed in sexual slang and unafraid to joke about it even between themselves.
- Dwindling Party: Tommy is the first to bite the dust when the beavers make a tree fall on him and crush him (he apparently is revived as a zombie later, but is still pinned to the ground and unable to move), then the neighbors are found out to be dead and turn into zombies later. Jenn and Buck, who had encounters with the beavers earlier, turn soon thereafter, Beaver!Buck kills Smyth and Beaver!Jenn kills Sam. After Mary and Zoe manage to drive off, Mary starts to turn and Zoe kills her. Ultimately, Zoe herself is run over by the truckers from the beginning of the movie.
- Exactly What It Says on the Tin: The movie does in fact have zombie beavers in it.
- Explain, Explain... Oh, Crap!: When Mary and Jenn read up on beavers, having boarded up the cabin, and learn they are good at tunneling.
- Final Girl: Zoe of all people! But not for long...
- Foreshadowing: Smyth's speech about beaver fever also infecting humans becomes relevant soon enough.
- From Bad to Worse: In The Stinger a bee comes into contact with infected blood, and then infects its entire hive. Now imagine the consequences...
- Groin Attack: Beaver!Jenn kills Sam by biting his penis off.
- Killed Offscreen: The neighbors.
- Mistaken for Flirting: At one point Jenn comes into Mary's room as though trying to be seductive, prompting Mary to wonder if she was angry about Sam cheating because it was her rather than because he cheated, but Mary protests that she doesn't think of Jenn that way... before Jenn starts to transform into a part-beaver herself.
- No Animals Were Harmed: "... in the making of this film, although the bear did receive a purple nurple (not our fault, he started it)"
- Our Zombies Are Different: Well organized and highly intelligent zombie beavers, whose bites or even scratches can turn humans into human-beaver creatures. Bears, too. And bees.
- Phoneaholic Teenager: Jenn and Zoe freak out when they discover their phones get no reception at the cabin.
- Raising the Steaks: Zombie beavers.
- Red Herring: Smyth the creepy hunter and the bear look like they will be trouble later on. In fact, no. Smyth sincerely tries to help the gang out, and the bear never actually does anything.
- Right Through His Pants: Mary and Sam start having terror sex, and in the next shot when zombies break through the floor they are both wearing underpants.
- Sacrificial Lamb: Zoe's dog Gosling, thrown into the water by the gang to distract the beavers while they swim from the raft to dry land.
- Suicide Attack: One of the beavers sets itself on fire only to run into a curtain and set fire to the entire cabin.
- Unwitting Instigator of Doom: The two truckers who accidentally dump the canister of chemicals into the lake, causing the beavers to mutate.
- Wham Shot: Jenn suddenly mutating into a beaver-zombie for two reasons: she was the Decoy Protagonist, and the reveal that the zombie beavers are contagious comes out as a surprise if only because it is shown really late into the movie.
- Zombie Infectee: Towards the end of the movie, Mary and Sam undress in front of each other to make sure neither of them has any bites or scratch marks. It turns out to be for nothing, as Sam gets bitten moments later, and Mary turns out to have been infected by contact with Beaver!Jenn's saliva.
