Joe and Lois Curtis (defendants) executed an oil and gas lease that provided for termination on October 4, 1947, unless construction of a well commenced before that date or the lessee paid the Curtises an annual delay rental. Phillips Petroleum Company (Phillips) (plaintiff) acquired the lessee’s interest in the lease. No well was constructed on the property, but Phillips paid the first delay rental by October 4, 1947. Phillips did not pay a delay rental for the following year by October 4, 1948, due to an inadvertent error made by one of its employees. But for the error, Phillips was willing and able to pay the delay rental on time. When Phillips discovered the error in December 1948, it submitted payment of a delay rental to the Curtises, but the Curtises refused payment and asserted that the lease had terminated. Phillips sued to quiet title to the lease. The trial court ruled in favor of the Curtises, and Phillips appealed.