He hit the water with a splash. His broad back smacked the water with the noise of a loud handclap. Biff could feel his back sting from the impact. He turned over and looked up. There was the bow of the boat, directly overhead. There was Li, looking down at him. “You all right, Biff?” There was a strange sound in Li’s voice. For a moment, Biff was angered. The strange sound was Li trying to hold back his laughter. Biff’s sense of humor came to his rescue. He must have been a funny sight, thrashing around in the water on his back like a beached porpoise. “Yep. I’m all right,” he called. “I’ll swim to midships. You can give me a hand up.” Once back aboard, Biff’s first concern was about the prowler. “Oh, him,” Li said. “When you made your backward bellywhopper, that guy took off. He raced down the dock. He’s long gone by now.” Biff rubbed the small of his back with his left hand. “That hurt. And here you are laughing at me.” “You were funny, Biff,” Li laughed. “And that sting won’t last long.” “Guess you’re right. Hey, let’s see if we can find out what our visitor was doing on board.” First the boys explored the deck of the boat. They opened the sail-chest and inspected the sails. They hadn’t been touched. They carefully examined the yawl’s rigging. Both knew that an important rope could be cut just far enough through so that it would hold in a mild wind, then snap in a heavy one, just when it was most badly needed. No evidence of any tampering with the rigging. “Let’s go below. That’s where the prowler was when we got here. He must have been doing his dirty work down there,” Biff said. A careful search of the cabins, each with two berths, revealed nothing. “Hey, look at this!” Li called. He was in the engine compartment, a small space between the forward cabin and the galley. “Doesn’t it look to you as if this has been moved recently?” Li pointed to the wooden cover which housed the engine. It was sitting slightly askew. “We’ll take a look underneath.” Biff took one side of the housing, Li the other. “Careful now. Heave gently.”