Yale law professor Ian Ayres examines Market Street Associates Limited Partnership v. Frey, a contract case turning on the duty of good faith in performance. The lecture walks through Judge Posner's reasoning in the opinion, unpacking how courts decide whether a party's conduct during an option exercise or renegotiation violates good faith obligations even when the contract's literal terms are followed. Ayres uses the case to illustrate the tension between opportunistic behavior and legitimate self interested dealing, a recurring theme in his American Contract Law course. The segment is part of a Coursera-linked lecture series and assumes some familiarity with the earlier material on contract formation and performance. It runs a little over a quarter hour and is built for students working through the doctrine case by case rather than casual viewers.