Miss Birks's birthday fell on the 1st April, and so did Betty Scott's. It was not a particularly happy date for an anniversary, but they both declared they liked it. To Betty it was certainly a chequered event, for the girls treated her to the jokes they dared not play on the head-mistress, and she had to endure a double dose of chaffing. But, on the other hand, a birthday shared with Miss Birks was luck above the common. There was invariably a whole holiday, and some special treat to celebrate the occasion. The nature of the festival depended so entirely upon the day that it was not generally decided till the last minute, which added an element of surprise, and on the whole enhanced the enjoyment. Whether this year's jollification would be outdoors or indoors was naturally a subject of much speculation, but the morning itself settled the question. Such a clear blue sky, such brilliant sunshine, and so calm a sea pointed emphatically to an excursion by water, and Miss Birks at once decided to hire boats, and take the school for a picnic to a little group of islets due west of the headland. The girls loved being on the sea, and did not often get an opportunity of gratifying their nautical tendencies, for they were, of course, never allowed to hire boats on their own account. Miss Birks was too afraid of accidents to permit lessons in rowing, though many of her pupils thirsted to try their skill with the oars, and had often vainly begged leave to learn in the harbour. To-day three small yachts, with steady and experienced boatmen, were waiting by the quay at Pontperran, and even Mademoiselle—the champion of timorous fears—stepped inside without any nervous dread of going to the bottom of the ocean. It was delightful skimming out over the dancing, shining water, so smooth that the worst sailor could not experience a qualm, yet lapping gently against the bows as if it were trying to leap up and investigate the cargo of fair maidens carried on its bosom. With one accord the girls struck up some boat songs, and the strains of "Row, brothers, row!" or

rang clear and sweet in the fresh spring air.

Everybody agreed that the passage was too short, and they were almost sorry when they arrived at their destination. The islands were nothing more than a group of five rocks, too small for cultivation, and inhabited only by sea-birds. Some rough grass and bushes grew on the largest, where there was also a shelving sandy strip of beach that formed a safe landing-place. Here all disembarked, and the provision hampers were carried ashore, together with the big iron trivet and cauldron used for picnics. There was something very fascinating in thus taking possession of a desert island, if only for a few hours. For the present the school felt themselves a band of girl Crusoes, and set to work at once in pioneer fashion to make preparations for lunch. There was an ample supply of drift-wood lying above high-water mark to serve as fuel under their trivet, so while some got the fire going, others took garden spades which they had brought with them and dug sand seats sufficient to accommodate the company. The chairs destined for the mistresses were quite superior erections, provided with backs, and that of Miss Birks was adorned with shells, specially collected from the rocks by a committee of decoration told off for the purpose. In shape and elaboration of ornament it resembled a throne, and as a finishing touch the motto "A Happy Birthday" was placed in yellow periwinkles at the foot.

By the time these extensive preparations were finished, the cauldron was boiling, for the fire had been well kept up, and replenished with wood. Miss Harding dropped in the muslin bag containing the tea, Jessie Macpherson assumed command of the milk can, and a willing army carried cups and laid out provisions. The boatmen were provided each with a steaming pint mug of tea, and a basket of comestibles amongst them, and retired to one of the yachts with grins of satisfaction on their countenances. That hospitality having been settled, the cauldron—which combined the function of urn as well—flowed busily, filling cup after cup till the whole school collected on the sand seats to do justice to the provisions. There were rival birthday cakes: Miss Birks's, a nobly-iced erection decorated with candied violets, was perhaps the larger of the two, but Betty's—sent from home—had the glory of fifteen coloured candles.

"Yours ought to have had candles too, Miss Birks," she said, as she carefully struck a match.

"I'm afraid they'd be too thick on the ground!" laughed Miss Birks. "I used to have them when I was a child, but I barred the exhibition of my years after I was twenty-one."

"I once knew a gentleman who had a huge birthday cake with seventy candles on, and all his grandchildren came to his party," volunteered Hilda Marriott.

"That must have been a truly patriarchal cake, and something to remember. I'm afraid I can only offer you candied violets. Betty, shall we each cut our first slice at the same moment? Here's to everybody's health and prosperity and good luck for the rest of the year!"

It was the first real picnic since last autumn, so, added to the double birthday, it seemed a more than ordinary festivity, and everybody waxed particularly jolly. Miss Birks told humorous Irish stories, and made endless jokes; even Miss Harding, usually the pink of propriety, was guilty of an intentional pun. The merry meal was over at last, and when the baskets had been repacked, all dispersed to wander round the tiny island. It did not differ particularly from the mainland, but the girls found it amusing to investigate new coves, and ramble about on the grassy expanse at the top of the cliffs. A few sought out Miss Birks and begged to be allowed to explore the next largest islet of the group, so after a little discussion half a dozen were sent off under charge of Miss Harding in one of the boats. As there only remained about forty minutes before it would be necessary to go back, it was arranged that this boat should not waste time by returning to the bigger island, but should start on its own account, independently of the other two, as soon as its party had made a brief survey of the islet.

Deirdre and Dulcie, who were venturesome climbers, took advantage of the extra liberty allowed them on this special day to escape by themselves without the tiresome addition of the usual third, and scaled the very highest point of the rocky centre. Here they found they had an excellent view of the whole of the small group, and could command a prospect of cove and inlet quite unattainable from the shore. Dulcie had brought a pair of field-glasses, and with their aid distant objects drew near, and what seemed mere specks to the ordinary vision proved to be sea-birds, preening their wings, or resting upon the rocks. They watched with great interest the progress of the boat to the other island.

"Didn't know Miss Birks was going to let anyone go, or we'd have gone ourselves," lamented Deirdre. "Who's in her? Can you see?" "Perfectly. Miss Harding and Jessie Macpherson, Phyllis Rowland, Doris Patterson, Rhoda Wilkins, Irene Jordan, and Gerda Thorwaldson. David Essery is rowing them."

"Oh, I wish we'd gone!" repeated Deirdre enviously. "Give me the glasses, and let me take a look."

It was a very long look, that swept all round the islands and took in every detail of cliff and rock. Deirdre repeated it twice, then gave a sudden exclamation.

"Dulcie, you see that big black cliff over there—rather like a seal—count three points farther on, and tell me if you don't think there's a boat in that tiny inlet."

Dulcie seized the glasses, and proceeded to verify the statement.

"It is! Oh, it certainly is! It's moving out now from behind the rock. Somebody's in it, rowing—Deirdre! I do believe——"

"Not him!" shrieked Deirdre ungrammatically, snatching the glasses from her friend. "Oh, it is! I'm perfectly persuaded it is! It's just his figure, and he rows in the same way exactly—the man in the brown jersey!"

"Then Gerda's engineered that expedition to go and meet him. It's as plain as plain!"

Their excitement was intense. It did indeed seem an important discovery, and an added link in their chain of circumstances. Should they stay where they were, and watch the meeting through the field-glasses, or would it be possible to follow the matter up more nearly? They resolved to make a try for the latter. Climbing down as rapidly as they could from their point of vantage, they found Miss Birks, and entreated to be allowed to join the party on the other island.

"John Pengelly would row us over, and we'd catch them up immediately," they pleaded. "Oh, do please let us go!"

Miss Birks was in a birthday frame of mind, and prepared to listen to any fairly-reasonable request.

"There would be quite room for you to go home in David Essery's boat," she acquiesced. "Yes, you may go if you wish. John Pengelly can take you at once. Tell Miss Harding I sent you, and you're to return with her party."

The boatman was good-natured, and apparently did not mind making the extra journey. He grinned at the girls as he pushed off.

"Can't have too much of the sea, missies?" he ventured. "I'll soon pull you over there."

He landed them carefully on the second island, then rowed back to the first landing-place to join his fellow boatman and smoke a pipe till it was time to start. Deirdre and Dulcie knew exactly which way Miss Harding and the girls had gone, and their plain duty was to follow them as rapidly as possible, and report themselves as additions to the party. They did nothing of the sort, however. Instead, they took exactly the opposite direction, and made for the western side of the islet, where they had seen the mysterious boat.

"You may depend upon it we shall find Gerda there," said Deirdre. "It's better not to let her know we're here. We're far more likely to catch her."

With a little scrambling they reached an inlet, which—so they calculated—must be the one they had marked through the field-glasses. They could see no boat, however, and no Gerda. They waited for a while, then rambled farther along the shore, but finding nothing, came back to their former point. They had so entirely counted upon Gerda being there that they felt decidedly disappointed.

"Perhaps she couldn't sneak off," suggested Dulcie. "Miss Harding's very tiresome and particular sometimes."

"I wonder if the boat's waiting about for her?" said Deirdre. "I should very much like to know."

Obeying a sudden impulse, she advanced to the edge of the waves and reproduced, as nearly as she could remember it, the long peculiar curlew cry which Gerda had given as a signal on the former occasion. The effect was instantaneous. There was an answering whistle, and from behind a rock not very far away a small craft shot out into the creek. It was undoubtedly the same white dinghy which they had seen before, and contained the same tall, fair man who had spoken with their school-mate. He rowed forward with a few rapid strokes, then seeing Deirdre and Dulcie he paused, took a searching glance round the shore, turned his boat, and rowed away from the island, passing as quickly as possible behind the shelter of the next of the group. Deirdre stood watching him through the field-glasses as he disappeared. She was not altogether sure whether she had not made a false move. It was perhaps hardly wise to have thus put him on his guard, and let him become aware that they knew of the curlew signal. She already regretted her hasty, thoughtless act. She was conscious that it would defeat her own ends. It seemed no use staying any longer in the creek, for he would certainly not be likely to return after such an alarm.

"We'd better go and find Miss Harding," suggested Dulcie.

It was undoubtedly high time they reported themselves, so, putting the field-glasses back in their case, they set off for the other side of the island. Arrived at the opposite cove, they looked eagerly for their school-mates, but nobody was to be seen.

"I expect they're a little farther on," suggested Deirdre, hiding the fear she dared not own.

But they were not farther on, and though the girls climbed the cliff, so as to have a thorough view of the shore, and shouted and cooeed till they were hoarse, there was not a sign of a human being anywhere. Far on the horizon were three tiny specks.

Dulcie took out the all-useful glasses, and adjusted the focus anxiously. One glance confirmed her worst apprehensions—the boats had gone, and left them behind! It was perfectly easy to see how it had happened. Miss Birks, having sent them specially across the sound, believed them to be with Miss Harding's party, and Miss Harding did not even know that they had left the larger island. It was their own fault entirely for not reporting themselves. While they had been watching the mysterious boatman on the wrong side of the island, the others must have been starting, utterly unconscious that two of their number were missing.

"We're marooned! That's what it amounts to." Deirdre's voice shook a little as she made the unwelcome admission.

"Well, of all idiots we're the biggest! We have got ourselves into a jolly fix!" exploded Dulcie.

It was highly probable that they would not be missed until the arrival at the harbour. Then, no doubt, someone would come back for them, but the tide was rising rapidly, and perhaps by the time a boat could return it would not be possible to land and take them off. The prospect of a night spent on a desert island was not enlivening. Then, too, came another fear. The mysterious stranger was in the near neighbourhood. Hidden behind rocks and creeks he might have accomplices, who might take it into their heads to reconnoitre. The idea was horrible. They felt an intense dread of the unknown man in the brown jersey. He must be very angry that they had discovered his signal. Suppose he were to find them, and wreak his vengeance upon them? They bitterly rued their folly, though that did not mend matters in the least.

"We won't go over to that side of the island again, in case he might see us," quavered Dulcie. "Let us sit down here, in this sheltered corner. How cold it's getting!" "I'm hungry, too," sighed Deirdre. "There's nothing to eat on the place except raw periwinkles!"

The sun had set behind a bank of grey clouds, and even in the last ten minutes the daylight had faded noticeably. A chilly wind had sprung up, and the girls shivered as they buttoned their coats closely.

"Do you hear something?" said Dulcie presently.

It was a sound of oars, and both pricked up their ears, half-nervously, half-hopefully. They did not venture to show themselves till they could ascertain whether it were friend or enemy. Hidden under the shadow of the rock, they watched the darkening water, then gripped each other's hands in terror—it was the white boat that appeared round the corner. Its brown-jerseyed occupant was rowing slowly and leisurely, with a careful eye on the shore as he went. Would he see them? They were only partially concealed, and a keen observer might easily detect their presence. To Deirdre those few minutes equalled years of agony—her lively imagination summoned up every possible horror. He paused at last on his oars, and gave the long shrill curlew call. A hundred seagulls screamed in reply. Twice, thrice he repeated it, then apparently judging it a failure, he rowed away in the direction of the mainland.

Dulcie was crying with fright and cold. She let the tears trickle unwiped down her plump cheeks. She was not cut out by nature for a heroine, and would gladly just then have given up all chance of seeing her portrait in the newspapers if she could have found herself safely back in the schoolroom at the Dower House. Adventures might be all very well in their way, but this one had gone decidedly too far.

"I wish you'd never suggested our coming," she said fretfully. "It was your fault, Deirdre."

"Don't be mean, and try and throw the blame on me! You were just as keen as I was!"

"I'm not keen now! I wish to goodness we'd never bothered our heads about Gerda. You won't catch me on such a wild-goose chase again!"

"I'm utterly disgusted with you, Dulcie Wilcox!" returned Deirdre witheringly; and Dulcie wept yet harder, to have added to her physical troubles a quarrel with her chum.

It was almost dark before a search party, consisting of Miss Birks and three boatmen, arrived to fetch them, and the tide had risen so high that it was impossible to land as before, so that John Pengelly had to wade through the water and carry each of them in turn on his back to the boat. Miss Birks said little, but they knew it was the ominous silence before a storm, and that she would have much to say on the morrow. They were intensely thankful when they at last saw the lights of Pontperran, and felt they were within measurable distance of food and fire.

"You provided a nice birthday treat for Miss Birks, I must say," commented Jessie Macpherson sarcastically. "What possessed you to go off on your own in that silly way? There was nothing in the least interesting on that side of the island, and you knew where we were, and that we should be starting almost directly. I simply can't understand such foolishness! Why did you do it?"

But an explanation of the motives that had influenced their conduct was the very last thing in the world that Deirdre and Dulcie felt disposed to offer, even to mitigate the scorn of the head girl.