Then it moved slowly up against the tide, rising and falling heavily upon the seas, but gaining a little, and then more.

It was enough. The spare anchor went overboard, the yacht brought up and held. They dropped the sails once more, unharmed, with the black, hungry reef stretching out its white arms of foam and spray, vainly, balked of their prey.

“O-oh!” said Harvey, sinking down on a seat. “That was a close shave. But what could have made that rope part? That’s what I can’t understand. It was a brand-new one.”

They found out a half-hour later, after they had gone below and put on their jackets and warmed themselves and had returned on deck. They drew the end of the line aboard and examined it by a lantern in the cabin.

It was not broken. The end was clean, without a frayed strand in it. It had been severed with a single sweep of a fisherman’s knife, sharp as a razor-blade.

“Ah!” ejaculated Harvey. “We might have guessed. It’s old Martel’s work. We’ll have the law on him for this.”

But when they peered across the water with the coming daylight there was no pink-stern sloop to be seen, because it had gone out with the tide long before, just as they went adrift, and was out upon the sea now, standing off to the eastward.

“Well, we have learned two lessons,” said Henry Burns. “One is to have the spare anchor where it can be got at quicker when it’s needed. I’d have gone for that first if I hadn’t remembered that we had it buried under that lot of stuff forward.”

“And what’s the other lesson?” asked Bob.

“It’s to be never without a knife when you are sailing a boat,” answered Henry Burns. “I heard a fisherman say that once, and so I bought one to wear in a belt aboard here. But I never thought just what it would mean to be without one when every second counts.”