In Counterpart, a TV series airing on the Starz network, everyone has a double. The show is set in present-day Berlin, three decades after the discovery of a portal to an alternate timeline—a world that diverged from ours in the late 1980s and now looks different in both subtle and radical ways.

The existence of the portal is a secret, but diplomats and spies traverse back and forth, trading intelligence and working operations with and against each other as factions and subfactions plot deeper conspiracies. Adding to the complexity is the fact that everyone has a second version of themselves, who may be an ally—or may be a murderous replacement.

The story is built around Harold Silk (a remarkable J.K. Simmons in a dual role), a low-level employee of the portal spy agency who encounters a tougher, crueler version of himself who is also a more effective agent. At heart, the show is a sci-fi riff on the Cold War, in which competing powers with overlapping histories jockey for position while trying to avoid all-out conflict.

It's a reminder of how much we tend to share with our enemies, and how our greatest rivals are often just twisted versions of ourselves.