Couchtuner The Enemy Within NBC Watch Series Online Free. In this character-based psychological thriller, Erica Shepherd (Jennifer Carpenter), a brilliant former CIA operative now known as one of the most notorious traitors in recent American history, is serving life in a Supermax prison. Against every fiber of his being, but with nowhere else to turn, FBI agent Will Keaton (Morris Chestnut) enlists Shepherd to help track down a fiercely dangerous and elusive criminal she knows all too well. While Shepherd and Keaton have different motivations for bringing the enemy to justice, they both know that to catch a spy… they must think like one.