“No hurry,” Sir Clinton pointed out, as Armadale and the constable quickened their steps. “We've got him trapped by the tide. There's only one bolt-hole—the cave. And I hope he takes it,” he added, with something of sinister enjoyment in his tone which surprised the inspector.
They moved leisurely in the direction of the cave-mouth; and, as they did so, the fugitive gave one backward glance and then splashed waist-deep through the water which was foaming into the entrance. He ducked under the low arch and vanished. As he did so, Sir Clinton halted, and then, after a careful inspection of the incoming tide, he led the way back to the car.
“It's as cheap sitting as standing,” he commented, settling himself comfortably in the driving-seat. “We'll need to wait here until the tide shuts the door on him by filling that tunnel he's gone through. After that, I suspect he'll be the most anxious of the lot of us.”
“But there's another exit from that cave,” Armadale pointed out. “He's probably climbing up the tube of the Blowhole just now, sir. He might get clean away by the top of the headland.”
Sir Clinton pulled out his case and lit a cigarette in a leisurely fashion.
“I'm sure I hope he does,” he replied, much to the inspector's surprise. “Just wait a moment and you'll see.”
He smoked for a minute or two without troubling to make his meaning clear; and then the souffleur itself gave the answer. Armadale's ear caught the sound of a deep gurgle from the heights above their head; then came a noise like a giant catching his breath; and at last from the Blowhole there shot up the column of spray, towering white and menacing in the moonlight. As it fell, Sir Clinton pressed the self-starter.
“That bolts the back door, you see, inspector. I only hope he's been caught on the threshold. Now, I think, we can go back to the hotel and see if we can pick up one or two useful things.”
He turned the car on the last strip of sand before the rocks and swung it round towards Neptune's Seat. After a little searching, he found a spot from which he could ascend to the road without straining his springs.
“I had the curiosity to examine that Blowhole cave at low tide once, inspector,” he explained as he drove up towards the hotel. “The thing works this way. The entrance is low, and the tide fills it soon. The air in the cave can still get out by a narrow tunnel leading up to the Blowhole. But in a minute or two this second tunnel's mouth gets filled up, and there's no escape from the cave. The sides are smooth, and the tide rises quickly, so that fellow will either drown or else he'll creep into the Blowhole tunnel to escape. The tide rises a bit farther, and compresses the air in the cave. At that stage the souffleur begins to work. Intermittently, you get the air-pressure in the cave big enough to blow through the Blowhole tunnel, carrying the layer of water there in front of it; and that mixture of water and compressed air makes the jet. So, you see, if that fellow's in the cave, he must be swimming round like a rat in a pail; and if he's in the tunnel, he must be suffering agonies as the jet comes up and tears at him. You know what sort of force it has. And if he can't cling on to the rocks of the tunnel, he'll be battered against the sides as the jet carries him before it, and he'll probably be severely injured by the time it spits him out at the top.”