Frederick Sunley (plaintiff) was the U.S. sales representative for a foreign steel mill. As he approached retirement, Sunley contracted with Manfred Wirth (defendant) to take over his duties. As part of this transaction, Sunley and Wirth signed a contract under which Sunley would act as Wirth’s agent and assist with Wirth’s sales. The contract authorized Sunley to take orders from customers on behalf of Wirth. Sunley brought suit for breach of contract, claiming that Wirth owed him certain sales commissions. Wirth claimed that Sunley accepted secret bribes from Non-Ferrous, one of Wirth’s customers, in exchange for increasing Non-Ferrous’s aluminum allocation. The district court found that the alleged bribes were irrelevant to the breach-of-contract claim and found in favor of Sunley. Wirth appealed.