What kind of phone scam could this be?

I just got the oddest phone call on my answering machine. Some guy says that I have to dial some 800 number because I am being charged by the treasury for some unspecified crime. The person gives his name but does not say what his position is and never mentions my name. I am tempted to dial the number, but prudence dictates that it would be best to just ignore it.

I can’t figure out what the deal is. I know that it can’t be legitimate, but I don’t know what kind of scam this could be. I am assuming that a phone number that begins 815 is toll free.