On these delightful breezy uplands, where the pleasant west wind blew fresh and warm from the Gulf Stream, Miss Birks's pupils might wander at will during play hours, only observing a few sensible restrictions. Dangerous climbs on the edge of the cliffs or over slippery rocks were forbidden, and not less than three girls must always be together. This last rule was a very necessary one in the circumstances, for in case of any accident to a member of the trio, it allowed one to stay with the sufferer and render any first aid possible, while the other went at topmost speed to lodge information at head-quarters. The old dwelling itself was a suitable and appropriate building for a school. Erected originally in the fourteenth century as a small nunnery, it had in the days of Edward VI fallen into the hands of the then lord of the Castle, who had turned it into a dower house. Successive generations of owners had in their time added to it or altered it, but had not spoilt its general atmosphere of mediaevalism. Little pieces of Perpendicular window tracery, or remains of archways were frequent in the old walls, and a ruined turreted gateway bore witness to the beauty of the ancient architecture. Nobody quite knew what vaults and cellars there might be under the house. Remains of blocked-up staircases had certainly been found, and many of the floors resounded with a suggestively hollow ring; but all tradition of these had been lost, and not even a legend lingered to gratify the curious. There was one element of mystery, however, which formed a perennial interest and a never-ending topic of conversation among the girls. In the centre of the first landing, right in the midst of the principal bedrooms, stood a perpetually-closed room. The heavy oak door was locked, and as an extra protection thick iron bars had been placed across and secured firmly to the jambs. Even the keyhole was stopped up, so that the most inquisitive eye could obtain no satisfaction. All that anybody knew was the fact that Mrs. Trevellyan, who had a well-deserved reputation for eccentricity, had caused a special clause to be made in the lease which she had granted to Miss Birks, stipulating for no interference with the barred room under pain of forfeiture of the entire agreement. "That means if we bored a hole through the door and peeped in the whole school would be turned out of the house," said Evie Bennett once when the subject was under discussion. "Even Miss Birks doesn't know what's inside," said Elyned Hughes with an awed shudder. "Mrs. Trevellyan wouldn't let the place on any other conditions. She said she'd rather have it empty first," added Annie Pridwell. "What can she have there?" "I'd give ten thousand pounds to find out!"