Hundreds of years from now, the last surviving humans discover the means of sending consciousness back through time, directly into people in the 21st century. These Travelers assume the lives of seemingly random people, while secretly working as teams to perform missions in order to save humanity from a terrible future.

These travelers are: FBI Special Agent Grant MacLaren, the team's leader; Marcy, a young, intellectually disabled woman in the care of her social worker, David; Trevor, a high school quarterback; Carly, a single mom in an abusive relationship; and Philip, a heroin-addicted college student.

Armed only with their knowledge of history and an archive of social media profiles, the travelers discover that 21st century lives and relationships are as much a challenge as their high-stakes missions.