In the country of Zouman, in Persia, there lived a Greek king who suffered from leprosy. All his physicians had failed to cure him until a learned physician named Douban arrived at his court.
Douban was versed in many languages and knowledgeable about herbs and medicines. Upon hearing of the king's ailment, he presented himself and promised a cure without conventional medicine, relying solely on the king's compliance with his instructions. Intrigued, the king promised great wealth to Douban and his descendants if successful.
The physician crafted a hollow-handled polo club, filled it with a special remedy, and made a ball. The next day, he instructed the king to play polo until his body grew warm, allowing the remedy in the handle to penetrate his system. Afterward, the king was to bathe and rest.
The king followed the instructions diligently. The following morning, he awoke to find himself completely cured, to the astonishment and joy of the entire court. Overwhelmed with gratitude, the king honored Douban richly, seating him beside the throne and bestowing upon him robes of state and two thousand sequins.
However, the king's grand vizier, a man of avarice and envy, grew jealous of Douban's favor. Determined to ruin the physician, he privately warned the king against trusting an unproven stranger, suggesting Douban might be an assassin.
The king dismissed these suspicions, defending Douban's virtue and pointing out the illogic of curing him only to kill him. He then recalled a story a vizier once told King Sindbad about the dangers of believing a mother-in-law's tales, piquing the jealous vizier's curiosity.