Where the parties to a contract come to an agreement which is reduced to writing by a third person, who makes a mistake in so doing, relief may be obtained in equity. Mutuality of mistake is necessary here as elsewhere; that is, the contract as written must fail to express the intention of either party to the contract.7 If, however, the written instrument failed to express the agreement of the parties, the right to relief will not be defeated because one party discovered the mistake before signing, and failed to disclose it to the other.8