Every year off the northernmost coast of the Gulf of Alaska, thousands of salmon sharks intercept millions of Pacific salmon on their run toward the spawning grounds of Prince William Sound. The film follows both sides of that collision, tracking the salmon as they push upstream against exhaustion and the sharks as they gorge on the run. Salmon sharks are the detail worth knowing here: unlike most of the roughly 500 shark species, they are warm-blooded, a trait that lets them hunt effectively in water cold enough to stop other predators. Underwater camera work stays close to the feeding itself, watching sharks cut through schools of salmon in open water and shallow river mouths where the fish have nowhere to hide. The stakes are stated plainly rather than dramatized: the salmon are driven by the need to reproduce before they die, the sharks by simple hunger. It is a portrait of one predator built for one narrow, brutal window of opportunity each year.