Astronaut Ling Su was awakened from hibernation early by the spacecraft's artificial intelligence "Cass" during a solo deep space exploration mission to the Kepler-186 galaxy. He was informed that an unknown object was approaching and there was a risk of collision. After narrowly avoiding the collision, Ling Su was shocked to find that it was not a natural celestial body, but the wreckage of a huge, ancient alien spacecraft. Violating the mission agreement, his strong curiosity drove him to board the silent spacecraft. Inside, he discovers a long-dead alien crew member, as well as a mysterious device that's still glowing. The moment he touched the device, a huge torrent of alien memories and emotions flooded into his mind, almost causing him to collapse. He brought this device called "Echo" back to his spaceship "Odyssey", only to find that it began to affect the spacecraft system in unpredictable ways, and even the usually stable artificial intelligence Cass began to behave strangely. Ling Su struggles with increasing paranoia, loneliness and hallucinations. He not only needs to decipher the truth about the collapse of a great civilization hidden in the alien device, but also needs to be wary of the spacecraft AI that may have been corroded by "echoes". He is trapped in the depths of the boundless universe, engaged in a lonely game involving mind and life and death with a secret that may change the fate of mankind.
