Hundreds of years in the future, the last surviving humans discover a way of sending consciousness back through time, directly into people in the 21st century -- "travelers," who assume the lives of seemingly random people. They're also secretly working as teams to perform missions in order to save humanity from a terrible future. Armed only with their knowledge of history and an archive of social media profiles, the travelers -- who include an FBI agent, a single mother and a college student -- discover that 21st-century relationships are as much of a challenge as their high-stakes missions.