If you're not a fan of spoilers, you may want to hold off on this brief guide until experiencing "Upstream Color" for yourself. But rather than provide all the answers, the items below are intended to break down some of the crucial story ingredients in the movie so that confusion over the details won't obscure viewers' engagement with its potent ideas. There's no question that certain parts of "Upstream Color" are difficult to comprehend, but at least these ingredients should help clear up some of the foggier bits. Of course, some of them are open to interpretation. Readers are encouraged to offer their own theories in the comments.
Those gross bugs feed on consciousness. In the unsettling opening act, Kris (Amy Seimetz) is attacked in a parking lot and forced to ingest a parasitic bug that makes its way into her bloodstream. Once there, it multiplies and achieves two functions: absorbing her consciousness and making her highly susceptible to hypnotic suggestion. According to Carruth, the idea was partly inspired by real-life parasites that have been documented for their ability to control the behavior of other entities. "There are these parasites that burrow into the heads of wasps and ants and make them fly erratically or climb to the top of trees and throw themselves off in order to benefit from something else, maybe a fungus on the forest floor," he told Indiewire. In this case, the bug is used to service the agenda of a mysterious figure identified only in the credits as The Thief.
Why is Kris copying down "Walden"? Among the many beguiling ingredients of "Upstream Color" is the recurring presence of Henry David Thoreau's "Walden; or, A Life in the Woods," a book-length essay published in 1854 in which the author documents two years of his life living in a cabin. While under the spell of The Thief, Kris is forced to copy down the entire book by hand, probably as a means of keeping her mind busy while The Thief gets some rest (at least, that seems to be the most plausible explanation). But this case of hypnotic trickery also serves the underlying ideas. Towards the end of the film, as Kris begins to come to terms with what has happened to her, she repeats several verses from the book by memory. This indicates that her recollections of the kidnapping experience have started to return to her.
The Sampler is basically a power freak. After The Thief has finished stealing Kris' money, another ominous man whom the credits identify as The Sampler (Andrew Sensenig) kidnaps her and takes her to a remote medical trailer for a bizarre operation in which he removes the bug from her body and implants it into a piglets. Using highly expressionistic imagery, Carruth makes it clear that an element of Kris' consciousness has been transferred to the animal (and via versa). But that's not all: By virtue of obtaining possession of the bug, The Sampler is able to continue to impact Kris' experience with her surroundings -- not unlike what The Thief did. But The Sampler's agenda is quite different. Rather than merely take advantage of her resources, he wants to continue to influence her consciousness, toying with her awareness by creating various sounds and sensations in his remote location that impact her waking life. In essence, he's playing god.
About those piglets. While not exactly characters in the movie, the piglets contain a representative power that culminates when The Sampler hurls several of them into a stream in the final, wordless act. According to PETA, "tens of thousands" of piglets are subjected to laboratory experiments each year. The Sampler uses them as vessels for his nefarious agenda, but as the plights of Kris and Jeff illustrate, the piglets endure as much turmoil as the people to whom they're connected, a point that serves the movie's weighty cycle-of-life conceits.
Orchids. Like the piglets, the orchids are eventually implanted with some aspect of the identities of the people originally subsumed by the bugs. When the pigletss are thrown into the river, the blue material that comes out of their bodies enters into plant roots, illustrating the resilience of both man and nature -- two side of the same coin, Carruth appears to be saying.
Thus, the coins. While regaining her memories and awareness of the ordeal she was put through, Kris repeatedly grabs coins dropped into a poll by Jeff and brings them to the surface. These can be easily read as nuggets of wisdom that collectively form the rich ingredients of consciousness that "Upstream Color" celebrates in its elaborate audiovisual design. UPDATE: Commenters point out that Kris is actually rescuing rocks, not coins, although we stand by this interpretation of their figurative dimension.
Kris' fluctuating emotions are a metaphor for maternal anxieties. Kris doesn't realize she has been psychically linked with the piglets, but Carruth views this symbiotic connection as a parental bond. "Kris is on a path to basically get to a psychic break," he told the science fiction site iO9. "She is dealing with the mania and hysteria of having her children be taken from her, without her ever being able to consciously know that she even has children."
"Upstream Color" is about free will. By the end of the movie, Kris and Jeff both fight back against The Sampler and regain control over their world. The movie's final scenes symbolize the celebratory feeling of taking control over one's destiny.