A couple travels to Sweden to visit a rural hometown's fabled mid-summer festival. What begins as an idyllic retreat quickly devolves into an increasingly violent and bizarre competition at the hands of a pagan cult.
Longtime couple Lori and Doug break up just days before Lori's little sister Bea's wedding to Jayson. In order to not disrupt the fun, they decide to pretend they're still together until the weekend is over.
Two scientists who share a romantic history are tasked with investigating unnatural animal behaviour on the site of a Manson Family-style cult's compound.