Is there any mistake in these sentences?

Paul's room and Judy's room share a circuit breaker. When the breaker is thrown, one of them turns off an appliance and goes downstairs to throw it. She used all three power-sources of the room and unplugged all the unused appliances but the breaker was thrown when he powered on an appliance. He knocked hard on her door but she did not answer because she already did all that she could do and thought quarrel was inevitable and possibly she would be punched. Paul kept knocking hard and calling her name loudly till she called emergency.