In Dolls, the idea is that due to massive immigration and other population problems, crime has hit an all time high and all the prisons are full. So a new controversial act (the ROT act I think they called it) was passed so that the murderers still on the street could be tried and convicted before they've been caught. And along with that a new police force of a few, highly skilled individuals are trained to hunt and kill these convicted felons still on the loose. Some people see them as keepers of the peace, others see them as "Dolls", emotionless killing machines, and so they hunt after these special units when they're on duty. And so far the story takes place from the perspective of the first brigade of this new force.