The contestants participate in a Reward Challenge for a barbecue by swinging along a rope course. For Immunity, they become pieces on a huge board game called �Squared Off.� �It’s the equivalent of playing chess with eight people,� says host Jeff Probst. Also, one of the contestants celebrates a birthday �by running around in [his or her] birthday suit all day long, which causes a lot of excitement,� says Probst. And a ninth person is voted off the island.