The granny is on the floor covered by blood and with a knife in the chest and the creature under your control is responsible for this. So you go backwards to find out what happened and what justifies you.
Another average point-and-click adventure game? Not at all! REW may have content that can be called standard. You click on things in the right order to get over holes, dangers or get rid of some monster. But the whole storyline goes backward so you can follow the story of the past and you find out what happened.