Getting into the city was surprisingly easy. The guards asked the twins what their business was when they got to the front of the line. They said they were shopping for herbs for their mother's garden who lives outside the city. Once inside, the harder part began. They had seven doses of a potion that would allow them to tell if anyone was a shapeshifter by looking at them. The problem was how it did this. The potion would last an hour, but the way it worked was that it transformed the drinker into a copy of the person they were looking at. It would always mirror the true form, hence why it would reveal the true form of a shapeshifter. The problem, of course, was that it meant the drinker would need to not be seen, or the guards would think the drinker was the shapeshifter, not the target. The twins would need to find a hidden position where they could observe many people at once, and hope the guards would not discover them while they tried to root out the shapeshifters.
They mapped out several locations in the city that would cover the majority of where people congregated. It would not catch everyone in the city, but if they were lucky, they wouldn't need it to. If the shapechangers wished to pave the way for an invasion, they would need to insinuate themselves into communities. Get people to trust them. So that betrayal would be unthinkable. The first location they checked was...