Great Lakes and European Lines, Inc. (GLE) (plaintiff), an international shipping line, secured a $3 million loan from Continental Illinois National Bank & Trust Company of Chicago (the Bank) (defendant) that was personally guaranteed by Fred and Helen Sahadi (plaintiff). After the business relationship between plaintiffs and the Bank deteriorated the parties entered into a contract to transfer the loan to another lender upon GLE’s payment of all outstanding interest to the Bank. A provision of the contract allowed the Bank to demand payment of the loan in full if plaintiffs failed to make an interest payment by the 15th day of each month. Thereafter, the Bank demanded full payment of the loan and interest when plaintiffs failed to timely make an interest payment. The Sahadis filed suit against the Bank in federal district court seeking release from their personal guarantee of GLE’s loan. The Bank argued that plaintiffs materially breached the agreement by failing to tender payment by the due date. The district court agreed and granted partial summary judgment in favor of the Bank. Plaintiffs appealed.