Counterpart is a new scifi/spy/thriller series from STARZ starring JK Simmons as two very different men who live in two different versions of the same world. The worlds are connected by a secret passage in Berlin that’s heavily guarded and controlled by the two world’s governments. Up until 30 years ago, there was one world, but then scientists caused it to split into two branching realities. The politics of each world spill over into the other world, causing friction and intrigue.
Each person has an “other” in the alternate reality, a duplicate self who may be nothing like themselves. The other self frequently becomes a target of political plots originated on the opposite side. Since the alternate realities have been kept a secret from the general public on both sides, this can cause some confusion.