How do you get ashes out of a white couch?

Some idiot came over this weekend and ended up wasting an ashtray on my white couch. I tried blotting it after i got the ashes up with a kirby, i tried like 4 different types of upholstery to get it out and there is still a spot, im a so mad im almost ready to go to jail, please help me before i go and let off some steam on his face and body.