What happened to the westing house on July 4th in book Westing Games?

In the book The Westing Games, the Westing House caught on fire on July 4th. The fire was intentionally set by Otis Amber, who was one of the heirs to the Westing estate. Otis had been jealous of his cousin Sam Westing, who had been favored by their grandfather. He set the fire in order to destroy the Westing House and get revenge on his cousin. The fire caused extensive damage to the house, and it was eventually torn down.