SIXTEEN Xan thought she caught the sound of thumping helicopter blades, but when she walked outside to check, the sky was disappointingly clear. It was only the jet boat's throbbing engines, as Baz brought the last supply run before the weekend. He waved from the wheelhouse and she waved back, wishing she had time to go for a spin in the Sound with him. It'd been weeks since she'd had time for a rollercoaster ride through the whirlpools, but she was dying to do it again. Soon, she promised herself. When the boat came back from dry dock next week. The freshly painted hull would slide across the surface better than the hydrofoil that belonged to one of the tour companies in town. The tide was in, so when Baz tied up the Argo, he only had to heft the boxes from the deck to the jetty inst