Counterpart

Howard Silk has spent years doing an unremarkable job in a Berlin office. Then Counterpart introduces him to a man who looks exactly like him and has lived a very different life. The organisation Howard barely understands sits across a boundary between two versions of the world.

J.K. Simmons makes the central idea work through behaviour rather than explanation. The two men do not simply wear different expressions; they listen, occupy a room and assess a threat differently. Watching them recognise what they share is as interesting as learning what separates them.

Around that performance is a patient espionage story of restricted information, compromised loyalties and institutions protecting their own arrangements. The speculative premise is taken seriously without requiring every scene to explain the machinery.

If an episode of Black Mirror has ever left you wanting a whole series to explore its idea, this is a good candidate. The Americans offers a related interest in identity as a daily performance, though without the science-fiction border crossing.