The four girls jumped up, and, hurrying off, went away round the rock with such record speed, that by the time Phyllis returned to fetch the remainder of the tent they were well out of sight. Imagining that they must have walked down the beach towards the village, Phyllis did not trouble to go and look for them, so the only person who knew the real direction they had taken was Patty, who happened to have overheard most of the conversation, and to have seen their hasty flight. Having examined as many sea anemones as she cared to, Patty climbed up a steep little track on to the cliff again, and spent a blissful half-hour by herself, lying in the sunshine on a bed of purple heath, watching the white sails of the boats in the distance, and a steamer far out on the horizon. From her point of lookout she had a very good view over the whole of the large bay. How fast the tide was flowing in! The sandbanks, which only ten minutes ago had gleamed yellow in the sunshine, were now covered with water, and a huge white wave appeared at the mouth of the estuary, advancing with threatening speed. "It must be the tidal wave that Phyllis spoke about," thought Patty. "She told us how dangerous it is on this coast, how it comes in with a great rush, as fast as a man can run, and floods all the bay quite suddenly. I expect that was the reason Miss Lincoln wouldn't let us go far along the beach this afternoon. Why! Surely that cannot be Muriel and the others such a long way out upon the sands! I thought they would have been back before now. Yes, it is! And their backs are turned to the sea! They're sauntering along as calmly as if the tide were going down instead of rising. Oh, why don't they look round and hurry?" Patty sprang to her feet and waved her handkerchief frantically, but the girls were not looking in her direction, and took no notice. What was she to do? She felt, at all costs, they must be warned. She would be obliged to disregard Miss Lincoln's orders, and to go along the beach and tell them of their danger. There was not time to run back and ask permission. Nobody else was in sight, so she must decide on her own authority that it was expedient for once to disobey. Scrambling quickly on to the shore by an even more precipitous path than the one by which she had ascended, Patty made what haste she could along the sands towards her companions. She shouted to them while she was still a considerable distance off, but though they waved their hands in reply, they did not come any the faster. "How stupid they are!" thought Patty. "Can't they see the water behind them? They walk as if they were strolling round the quad." With an extra effort she hurried on, and reached them out of breath and panting. "Why don't you make haste?" she gasped. "Didn't you hear me call?" "It's all very well to say 'Make haste!'" replied Maud. "We can't get Muriel along."