The cause of the fire that heavily damaged the boyhood home of novelist Thomas Wolfe last week was arson, an investigator said. Someone apparently threw an unidentified object through the dining room window to start the fire, said Harley Shuford of the Buncombe County Arson Task Force. The dining room sustained the worst damage. A $20,000 reward is being offered for information leading to an arrest. The house, the setting for Wolfe's classic "Look Homeward, Angel," was gutted by fire early Friday. The house has been a state historic site for 24 years. The blaze burned away most of the roof and broke through one side of the house.