Exit your front door to your Home and talk to Elazul(he should be there). Tell him you haven't seen Pearl and have him join you.
Enter the Mekiv Caverns. Talk to the duck and work your way through the caverns to battle the Jewel Beast. (Boss areas are marked on the map.)
Upon Completion: Return home, talk to Lil' Cactus, go downstairs (watch him write the Event on the leaf), and go back upstairs to save your game before continuing.