Charles nodded with the feeling that the ice was cracking beneath him.

“And how did it get back into the room afterwards?”

Charles paused to consider his reply, but the detective supplied it.

“The inference is fairly obvious,” he said.  “The key was found inside the study after the locked door was burst open.  It was your father who found it, on the floor.  At least, he pretended to find it there.  It was your father who started the suicide theory.”  He paused, then added in a smooth reflective voice, “Really, the whole thing was very ingenious.  It reflects much credit on both of you.”

Charles spoke with an air of sudden decision.

“My father did these things to shield me,” he said.  “I did not want to reveal that, but I see that concealment will only direct unmerited suspicion to him.  When I returned from Flint House that night I let myself in with my latchkey and went straight to my bedroom.  My clothes were wet through, and I lit a fire in my room to dry them.  As I was spreading them out in front of the blaze the key of the study dropped out of the waistcoat pocket on to the floor.  I had forgotten all about it till then.  I picked it up and placed it on the mantel-piece.

“Some time after I was aroused by my father entering the room.  He had come to tell me of my uncle’s death—­the news had just arrived from Flint House.  His face was very white.  ’Your uncle has been found dead—­shot in his study,’ he said.  I had jumped up when he came in and was standing in the centre of the room.  As he spoke his eyes travelled past me to my wet clothes in front of the fire, and then returned to my face with a strange expression.  ‘Did you go to Flint House?’ he asked sharply.  I could only nod.  ‘And did you see him—­your uncle?’ was his next question.  On that, I told him the truth—­told him what I had found.  I told him about locking the door, and showed him the key on the mantel-piece.  He slipped it in his pocket, then turned and gave me a terrible look.  ’I am going over to Flint House,’ he said, ‘but you had better stay here.’  And he left the room.”

“What time did you reach Flint House that night?” asked Barrant.

Charles Turold realized that the critical moment had come.  He had foreseen it when he saw the detective standing at the gate of Flint House.  The relation of Thalassa’s story to Barrant had carried with it the inevitable admission that Sisily was at Flint House on the night of her father’s death.  The point Charles had to decide was whether he should divulge the additional information that he had seen her leave Flint House with Thalassa on that night.  As he covered the space which intervened between him and Barrant waiting at the gate, he decided that the moment had come to tell all he knew.

“I know now that it couldn’t have been much after half-past eight,” he said in reply to Barrant’s question.

“Did you see Miss Turold there?”