The series follows a diverse cast of characters, primarily scientists, who all come into contact with an extraterrestrial civilisation, leading to various threats and humanity-wide changes. 

Ye Wenjie, a Chinese astrophysicist, runs into trouble with the authorities after witnessing her father's death during a struggle session in the Cultural Revolution. Due to her scientific background, she is sent to a secret military base racing against other countries to make first contact with aliens during the Cold War. While there, she makes a choice that impacts humanity's future. In present-day London, a series of mysterious suicides and science-averse phenomena lead a government investigator and a group of friends called the "Oxford Five" into a mystery of extraterrestrial origin.