At age 11, Helen disappeared in the wilderness of Mount Rainier National Park while camping with her father, Benjamin. She was gone for almost a week before being discovered and returned to her family. It is now 25 years later, and after more than two decades of estrangement, Helen and Benjamin reconnect to try to understand what happened during the days she was gone. Meanwhile, Benjamin meets a peculiar woman and boy who seem driven to help him learn more about Helen's disappearance. Passersthrough is a haunted, starkly lyrical exploration of the border between life and death.