I'm thinking about plying GRIMM, but I want to try before I buy.

Is there a free demo or something out there?

The closest thing we have to a pre-made module is the one from the old d20 system as opposed to the modern d6 system. (link for pdf for adventure here and characters here ). I suggest making your own characters because it'd be hard to try and convert them. Otherwise it's easy to convert, just determine which skill used in the d20 system falls into the few from the d6.