Abstract This article deals with a mosaic from ancient Zeugma on the Euphrates found in 2002 and recently published with interpretive commentary. Its subject is the story of Theonoe and Leukippe preserved only in Hyginus and nowhere in Greek. Despite this, the authors argue that the myth, in its unique form, can for over one thousand years be connected with romance, mime, pantomime, tragedy and derives ultimately from early Cretan rituals of transvestism. Its immediate inspiration however is imperial pantomime along with the transvestism notorious in that genre, as can be argued from the layout of the mosaic and the iconography of Theonoe, our first clear picture of a pantomime. But the main thrust of the article, especially in appendix B, is to demonstrate that the Hyginus story must now be considered to represent the plot of a lost tragedy, which derived many of its elements from late Euripides, but in its over-enthusiasic use of these represents a post-Euripidean artificially complex plot-type, for which hitherto we had limited evidence.