Until the female lead is revealed to be a grossly mutating shapeshifter who devours animals in order to keep her human appearance from dissolving into gooey ick, Spring could be mistaken for a relaxed little indie about budding love. In fact, the film’s idea seems to come from a jokey proposition: What if you were watching one of those walking-and-talking indie romances in the style of Richard Linklater’s Before series, and it suddenly turned into a horror flick? Though slowed by artiness and a certain overly earnest attitude, Spring manages to catch some of the appeal of such a genre-blending experiment.