ace of the upper wall; "unless he was bent on suicide, in which case
we should have found what was left of him at the foot of the tower."

As they went on round the house, Miss Morriston was seen coming up the
drive. Her brother hurried forward to meet her.

"I say, Edith," he exclaimed, "we are in a great fix. Can you explain
how the door of the top room in the tower comes to be locked with the
key inside?"

Miss Morriston looked surprised. "What, Dick?"

"We can't get in," Morriston explained. "We found the door locked and the
key missing, and then when Alfred tried another key, he found the right
one was in the lock but inside the room."

Miss Morriston thought a moment. "My dear Dick, the door can't be
locked."

"It is, I tell you," he returned; "most certainly locked. We have tried
it and found it quite fast."

"Then there must be someone in the room," his sister said.

"That," Morriston replied, "seems the only possible explanation. But I
shouted several times and got no answer."

"Someone playing you a trick," and the girl laughed.

"But who? who?" he returned.

His sister gave a shrug. "Oh, you'll find out soon enough," she replied,
with a smile.

"I shall," he replied, as two men appeared making for the servants'
entrance. "Here comes Henry with the locksmith."

Miss Morriston in her stately way looked amused.

"My dear old Dick, you have been making a fuss about it. You will
probably find the door open when you go up."

"And I'll know who has been playing this stupid trick," Morriston said
wrathfully.

"A footman making love to a housemaid turned the key in a panic at being
trapped," Kelson said to his host.

"I dare say," Morriston replied with a laugh of ill-humour. "And he'll
have to pay for his impudence."

That explanation by its feasibility was generally accepted as the simple
solution of the mystery.

"Come along!" Morriston called. "We'll all go up, and see whether the
door is open or not. We shall just be in time to catch the sunset."

He led the way through the hall and the corridor beyond and so up the
winding stairs.

"What, not open yet?" he exclaimed as the last turn showed the workman
busy at the lock. "Well, this is extraordinary."

The locksmith was kneeling and working at the door, while the footman
stood over him holding a candle.

"The key is in the lock, inside, isn't it?" Morriston asked.

"Yes, sir," the man answered. "There is no doubt about that."

"How