Complex sentence: Tom, meanwhile, walks away from the coal pile, but only his head is blackened, so his ruse doesn't fool Mammy, who begins to pelt pieces of coal angrily at him.
Split into simpler sentences: Tom, meanwhile, walks away from the coal pile, but only his head is blackened, so his ruse doesn't fool Mammy. Mammy begins to pelt pieces of coal angrily at him.