Every day in any country, in any city, people disappear. Disappearing into the darkness. No one, including the police, knows why or understands how this is happening. And soon almost everyone will forget about these missing people. Everything, but not Mila Vasquez. Seven years have passed, but the darkness does not let go of Mila, it leaves marks on her skin, perhaps because the roots of evil have reached out to her soul. Remembering the disappeared is her job. These people look at her from the walls of the Hall of Lost Steps.

But one day those who disappeared appear again. To kill. They look exactly the same as before. But Evil irrevocably changed them. The investigation into the crimes they committed reaches a dead end. And only Mila Vasquez is able to stop this army of shadows. She must give form to darkness, formulate a convincing rational theory... A theory of evil.