High school senior Rod Walker decides to take part in a test organized by a school for graduates— the final exam on solitary survival. Each student must pass through a tunnel connecting two spatial coordinates. On the outside side of the portal, completely unfamiliar terrain may appear—different climate, different life. There are no limits on the type of equipment a student can take, nor on its quantity. According to the exam rules, students must remain alive for several days until the portal opens again.