seller wants out of contract, end buyer has'nt closed

[Kevin Burton]

I have a house under contract with a seller of which ive assigned to an end buyer. The earnest money is already in escrow with the title company. the end buyer claims to be quieting the title. it is three weeks past the closing date we set on the contract and the seller keeps calling me wanting to close. after ive already told him that i assigned the contract. can he pull out even though it is in escrow?