Mehdi is a dancer from Shiraz, and was the prized male concubine of the recently deceased princely merchant Emir Hakam ibn al-Ashath, whom he reluctantly accompanied to Chang'an.

Due to the rather scandalous circumstances of the death, Mehdi is suspected by the late Emir's household in Chang'an of having poisoned his benefactor with cantharis, and now wants (as a matter of some urgency!) to return to Persia.