Wolf Trap (D) contracted with the Opera Company (P) for four performances of an opera, at a specified sum. D was obligated to provide the necessary facilities and lighting. Before the last performance, an electrical storm struck a power line and left the entire area without power. D recommended that the last performance be canceled for safety reasons. D never paid P for the last performance. P sued to recover payment for the last performance. The District Court rejected D's impossibility defense on the grounds that the occurrence of the storm was foreseeable. That court made a judgment for P. D appealed.