Mrs. Wilson's errand was evidently a long one. Though they relieved each other more than once in mounting guard over the keyhole, she did not return. "Perhaps she knows we're here, and won't come out till we've gone," suggested Lindsay at last. "How could she know?" "She may have been looking at us all the time through some little spy place." "Oh, how horrid! It makes me feel quite creepy to think of it." The fact that they were doing exactly the same did not strike either of the girls. Circumstances alter cases, and they considered they were justified in their plan of action. They grew extremely tired of waiting, but they were determined not to give in. "There's that noise again!" said Cicely. "She must have a prisoner shut up there; I'm perfectly certain about it." Both put their ears to the door, and were so absorbed in listening to the queer sounds inside the room that they did not hear footsteps sounding up the winding staircase. An exclamation behind them caused them to turn hastily round. There was Monica!--the last person in the world whom they had expected to see, and who was looking as astonished as themselves at the meeting. Lindsay and Cicely felt decidedly embarrassed. Monica must have seen them peeping through the keyhole, and they knew they had been discovered in a somewhat doubtful and discreditable occupation. They could not possibly begin to explain that it was entirely on her account and for her benefit, so they simply turned very red and said nothing. It was a most uncomfortable situation. There was a painful pause, and then Monica recovered her presence of mind. "Why, Lindsay and Cicely, I thought you were with the others in the garden!" she said. "We were only exploring the house a little," replied Lindsay, trying to pass the matter off carelessly. "Miss Russell said there were interesting things all over it." "I'm afraid you won't find much to interest you among empty bedrooms," said Monica, in her calm, quiet voice. "If you like to come downstairs with me I'll show you some of the curiosities in my cabinet. I've a great many old coins and a few daggers that were dug up when the moat was drained." Looking rather shamefaced, the pair went with Monica to the library, where she unlocked an oak cupboard, and spent quite twenty minutes in explaining her various treasures. She was most kind, and spared no trouble, but the others could not get over their confusion. They had the guilty sensation that they had been caught like naughty children, and were being amused to keep them out of the way. "Why was Monica going into the lantern room?" demanded Lindsay, the moment they were alone. "Does she know the secret?" ventured Cicely. "Either she knows, or she's trying to find out. Perhaps she's stalking Mrs. Wilson too!" This was a new idea, and required consideration. "Then that would perhaps be what 'The Griffin' was warning Scott about," said Cicely reflectively. "Ought we to tell Monica?"