A figure from ancient folklore, the doppelganger--in fiction a character's sinister look-alike--continues to appear in literature, television and film. The modern-day version (of the Doppelganger, or "double-goer" in German) is typically depicted in a form adapted to reflect present-day social anxieties. Focusing on a broad range of narratives, the author explores 21st century representations in novels (such as Audrey Niffenegger's Her Fearful Symmetry, Jose Saramago's The Double), television shows (Orphan Black, Battlestar Galactica, Ringer) and movies (The Island, The Prestige, Oblivion).