By 1857, Wagner had become infatuated with Mathilde. It is not known whether she returned his affections to the same degree, or if the affair - if there was one - was ever consummated. Nevertheless, the episode inspired Wagner to put aside his work on Der Ring des Nibelungen (which would not be resumed for the next twelve years) and begin work on Tristan und Isolde.
In 1858, Wagner’s wife Minna intercepted a romantic letter from Wagner to Mathilde. After the resulting confrontation, Wagner left Zürich alone, for Venice. Minna went to Dresden to stay with her family. She wrote to Mathilde before departing for Dresden: