Kurt fell and hurt his back as he came down, so you're on your own to clear out Team Rocket. The second Rocket Grunt is guarding a Super Potion. When you've defeated all four, you'll automatically find yourself back at Kurt's house above.
You can't move the boulder in the Northwest corner until you have Strength (HM04), and you can't get to the ladder in the Southwest corner until you have Surf (HM03). You will find TM18 (Rain Dance) and a King's Rock on the lower level when you do, so be sure to come back here!