The Grissoms owned and operated a hotel and restaurant as a Howard Johnson Company (HoJo) (defendant) franchise. The Hotel and Restaurant Employees Union (plaintiff) represented their employees in two bargaining units. Both collective-bargaining agreements (CBAs) required arbitration and bound successors. The Grissoms gave up their franchise and leased the property to HoJo to operate directly. HoJo wrote the Grissoms, stating it would not be bound by existing labor agreements. The Grissoms told all the employees they would be terminated in two weeks when HoJo took over operations. Two days later, HoJo notified the union it would not recognize it or assume CBA obligations. HoJo hired new employees and started operating with 45 employees, including nine who had worked for the Grissoms, but all supervisors were new. The union sued to compel HoJo to arbitrate, arguing the CBAs required HoJo to hire all the former Grissom employees. Both lower courts held HoJo had to arbitrate. The Supreme Court granted review.