The control system for The Rats in the Walls is very similar to that of any other traditional 2D graphic adventure. You can examine elements in the scenes, pick up objects, use objects with other elements and, of course, investigate the whole scene.
The goal of The Rats in the Walls is to figure out what happened in the mansion of your protagonist's ancestors, as it seems that something is very wrong from the very beginning of the game. It won't take long for you to discover that, in fact, many things went very wrong in the past.
The Rats in the Wall is a short, very interesting graphic adventure. Though it doesn't have particularly fun mechanics, it does tell a very unsettling story.