Buick Motor Co. (Buick) (defendant) is an automobile manufacturer. Buick sold an automobile to a retailer, who sold it to MacPherson (plaintiff). The automobile contained a defective wheel which had been manufactured by another company. The defect was unknown; however, Buick could have discovered the defect through a reasonable inspection. The defective wheel caused the automobile to collapse while MacPherson was driving, and he was injured. MacPherson brought suit against Buick for negligence. The lower court entered judgment for MacPherson and Buick appealed.