In 1977, Richard and Rebecca Worst (defendants) acquired a parcel of land, together with seven shares of Twin Falls Canal Company (Twin Falls) water. The southeast corner of the parcel had a culvert leading to an open ditch, which was previously used to irrigate water to the parcel. The Worsts never used water on the property and never inspected the ditches. To prevent losing access to the water, the Worsts arranged for a neighbor to farm the parcel in 1980 and 1981. The Worsts were unaware that the neighbor used his own waste water rather than irrigating water from Twin Falls. Consequently, water had not been irrigated from Twin Falls onto the parcel since 1977. In 1982, the Worsts listed the parcel and water shares for sale. Norris and Katherine Thieme (plaintiffs) visited the parcel and, upon observing the culvert and ditch, assumed that water could be irrigated to the parcel. In March 1983, the Thiemes purchased the parcel and water shares with the intent to build a home, pasture a few animals, and plant a garden. That spring, the Thiemes discovered a cement barrier preventing delivery of water into the ditch. Neither the Thiemes nor the Worsts had been aware of the obstruction. In November 1983, the Thiemes brought suit seeking a rescission of the sale. The trial court found that both parties mistakenly believed the water shares could be delivered to the parcel. As a remedy, the court modified the agreement to require the Worsts to arrange for water to be delivered to the parcel. Since the Worsts had not provided water, the court found the Worsts had breached the contract. Rather than grant the Thiemes’ request for rescission, the court required specific performance. The Thiemes appealed. The Worsts cross-appealed, arguing that a mutual mistake did not exist.