The imagistic, dreamlike and enigmatic qualities of Shane Carruth's follow-up to his 2004 time-travel mind-bender Primer are such that it is hard to find two viewers with the same interpretation of its plot.
But here's mine: there's a maggot-like parasite that, if introduced to the human body, secretes something psychoactive which imbues its host with an extreme empathy, bordering on telepathy. It also makes one highly suggestible, such that a character known here only as "the Thief" (Thiago Martins) can drug and kidnap graphic designer Kris (Amy Seimetz), rearrange her construction of reality, and get her to sign away her belongings.
Later, Kris meets Jeff (played by Carruth), to whom something similar has happened and to whom she feels a strong attachment. But how can she begin to trust him or her feelings for him when she can no longer trust subjective experience? Don't ask me how the character known as "the Sampler" (Andrew Sensenig) or all of the piglets are involved. It's a kind of alien-invasion movie told from the inside out, with strong echoes of Close Encounters of the Third Kind and more than one David Cronenberg film.
With its fractured, slippery narrative, one can imagine that the experience of watching it might be akin to paranoid schizophrenia, or of being on drugs. It looks real, but you can't trust it. And with its woozy ambient sound design and free-associative visuals, one can imagine it will be best enjoyed on drugs, too.
There's a valid criticism to be made of Carruth's refusal of narrative resolution; a frustrating sense that the film goes down some of the less interesting avenues that it opens up in the fascinating first half. But his storytelling ambition, his fierce independence (he wrote, directed, produced, scored, shot, edited, acted in, and – in the US – distributed it himself), and his faith in the audience, are fully commendable.