The city and the city

A detective investigates the murder of a young woman in a city that occupies the same physical space as another city, with citizens of each trained from birth to mentally "unsee" the other's existence. As the case deepens, it draws him across the fraught boundary between the two cities, threatening to destabilise the uneasy coexistence maintained by a shadowy enforcement authority. The investigation ultimately forces him to confront dangerous political conspiracies operating in the hidden overlap between the two worlds.