Russell (defendant) entered into a contract with Duff (plaintiff) to become a member of his opera company. Russell agreed to appear as a soprano for two seasons in any operas that Duff produced. Russell agreed to give seven performances a week. The agreement also provided that Duff would supply the costumes for the operas. The agreement did not explicitly provide that Russell could not perform in other shows. At the end of the second season, Russell not only refused to perform for Duff, but she had agreed to perform for a rival company. Russell complained that the costume Duff provided, namely the tights that she was required to wear, were unhealthy. Just before refusing to perform for Duff, Russell sent a letter to Duff informing him that she would perform in the upcoming opera, including wearing the required tights, if he would increase her pay. After Russell quit, Duff was unable to replace Russell for the remainder of the season with an actress and singer who had the same qualifications and reputation as Russell. Duff sought a preliminary injunction to enjoin Russell from performing for his rival. The injunction was granted. Russell appealed to the Superior Court of New York City to determine whether the injunction was proper.