Sinister, overpowering, otherworldly creatures have forced humanity into a lair of vast, underground bunker systems for decades. SUM1, a young military recruit, is sent to Earth’s surface to protect the last survivors in a remote forest from the watchtower of a security circle. On his 100-day mission, SUM1 faces opposition that changes his entire view of reality and throws him into an existential struggle for sanity and survival driven by paranoia and isolation.