He and Scotty had long ago agreed that four sounds underwater would be the danger signal. He reacted instantly. The fishing line was in a pocket on his equipment belt. He took it out and pulled line from the spool. Then, probing deeply with one hand, he pushed the line under the smooth object, reached across and down with the other hand. When his hands met, he passed the line from one to the other and pulled the line through. Now it was around the object. He tied the line quickly, then rolled over on his back and looked upward at the surface. He could gauge the position of the sun, even though he could see no details. Using the rays filtering through the murk as a guide, he oriented himself. "Which bank?" He thought quickly. Danger could only come from the mansion, and that was on the south bank. He turned and swam north, going slowly, paying out line from the spool. Now that he was traveling in a straight line, he covered the bottom quickly, and in less than a minute he was in shallow water. He stopped, afraid that his tank would show above the surface. It was clearer in the shallows. He made out the line of a branch, or root of some kind that thrust its way through the surface. It would serve. Quickly he passed the spool around it and made a knot, then he pushed the spool itself into the mud and turned. Now to find the boat again. Cruising slowly, he headed in the general direction, rising slightly as he swam. Finally, he found the boat by its shadow and swam under it to the stern. Again orienting himself by the sun, he made sure that the boat would be between him and the south bank. He surfaced and pulled off his mask. Scotty was swabbing the deck of the cockpit as casually as though trouble was the last thing on his mind. Rick wondered briefly if he had imagined the danger signal, or had mistaken some other sound for a signal. Then Scotty hailed him. "Where are all the clams?" Rick's mind raced. Obviously someone was listening. Was the someone on the boat, or ashore? "I only found one," he called back. "I don't believe there are enough in this cove to bother about, no matter what those fishermen said." "Did you dig deep enough?" Scotty asked. "As deep as I could without a shovel. The mud is two feet thick down there." "Well, you might as well come aboard. I guess if we're going to have clam chowder, we'll have to buy clams from a commercial boat." Scotty wouldn't invite him aboard if there was any danger, Rick knew. He accepted the hand Scotty held down and got aboard. He surveyed the situation quickly. There was no sign of any danger. "Pretty murky down there?" Scotty asked. "Like swimming in ink." "We'll try again out in deep water. It should be clear near the river mouth." "Suits me," Rick said. "I never did think we'd find clams in this cove. The mano boats dredge in deeper water than this."