The concept behind The Deed is a fairly simple one. It is a murder mystery in reverse. In other words, the player takes on the role, not of a detective trying to solve a crime, but instead the role of a murderer who must plan and then execute the perfect murder. Put simply, in The Deed, you need to kill someone and then pin it on someone else.
The core of this idea does correspond in some way to the clearly cerebral qualities of investigation. Like the detective, the murderer does need to think about motive and how motives are expressed through evidence, as well as things like how a murder weapon might best be connected to a perpetrator. However, the fascinating thing for me about playing The Deed is in recognizing how very much more concerned with morality I am when playing as a killer by contrast to how objective and distant taking on the role of the detective so often feels.