Two cities are in the same place but separated by boundaries seen and unseen. Besźel and Ul Qoma do not have a river or wall to define them. Instead the border goes beyond the physical and into the psychological, and it is so complete that each city has its own language, culture, and laws.

A young woman is found murdered in Besźel. At first, the speculation is that she was a prostitute killed by a violent client, but Inspector Tyador Borlú begins to believe that something is wrong with that scenario. The case begins to point to something far more complicated and dangerous. In The City & The City by China Mieville, Borlú searches for the truth, but finds he must cross the border to Ul Qoma in order to discover it. Though this novel stretches reality, it mirrors the gritty politics that can be very dangerous, especially for detectives who want to find a killer.