The Jewel of the Nile (1985)

In this sequel to "Romancing the Stone" Jack and Joan have their yacht and easy life, but they are gradually getting bored with each other and this way of life. Joan accepts an invitation to go to some Middle Eastern country as a guest of a sheikh, but there she is abducted and finds herself involved with the "jewel". Jack and his new partner Ralph attempt to rescue her. They all go from one adventure to another... What is the story of this "jewel"?