The Secret Adversary by Agatha Christie

Sir James nodded comprehendingly.

“Mrs. Vandemeyer was a woman of great personality. With that and her social position she would have had little difficulty in imposing her point of view in preference to yours. Your sensational accusations against her would not easily have found credence.”

“That’s what I thought. It ended in my being sent to a sanatorium at Bournemouth. I couldn’t make up my mind at first whether it was a sham affair or genuine. A hospital nurse had charge of me. I was a special patient. She seemed so nice and normal that at last I determined to confide in her. A merciful providence just saved me in time from falling into the trap. My door happened to be ajar, and I heard her talking to some one in the passage. SHE WAS ONE OF THEM! They still fancied it might be a bluff on my part, and she was put in charge of me to make sure! After that, my nerve went completely. I dared trust nobody.

“I think I almost hypnotized myself. After a while, I almost forgot that I was really Jane Finn. I was so bent on playing the part of Janet Vandemeyer that my nerves began to play me tricks. I became really ill–for months I sank into a sort of stupor. I felt sure I should die soon, and that nothing really mattered. A sane person shut up in a lunatic asylum often ends by becoming insane, they say. I guess I was like that. Playing my part had become second nature to me. I wasn’t even unhappy in the end–just apathetic. Nothing seemed to matter. And the years went on.

“And then suddenly things seemed to change. Mrs. Vandemeyer came down from London. She and the doctor asked me questions, experimented with various treatments. There was some talk of sending me to a specialist in Paris. In the end, they did not dare risk it. I overheard something that seemed to show that other people–friends–were looking for me. I learnt later that the nurse who had looked after me went to Paris, and consulted a specialist, representing herself to be me. He put her through some searching tests, and exposed her loss of memory to be fraudulent; but she had taken a note of his methods and reproduced them on me. I dare say I couldn’t have deceived the specialist for a minute–a man who has made a lifelong study of a thing is unique–but I managed once again to hold my own with them. The fact that I’d not thought of myself as Jane Finn for so long made it easier.

“One night I was whisked off to London at a moment’s notice. They took me back to the house in Soho. Once I got away from the sanatorium I felt different–as though something in me that had been buried for a long time was waking up again.

“They sent me in to wait on Mr. Beresford. (Of course I didn’t know his name then.) I was suspicious–I thought it was another trap. But he looked so honest, I could hardly believe it. However, I was careful in all I said, for I knew we could be overheard. There’s a small hole, high up in the wall.

“But on the Sunday afternoon a message was brought to the house. They were all very disturbed. Without their knowing, I listened. Word had come that he was to be killed. I needn’t tell the next part, because you know it. I thought I’d have time to rush up and get the papers from their hiding-place, but I was caught. So I screamed out that he was escaping, and I said I wanted to go back to Marguerite. I shouted the name three times very loud. I knew the others would think I meant Mrs. Vandemeyer, but I hoped it might make Mr. Beresford think of the picture. He’d unhooked one the first day–that’s what made me hesitate to trust him.”

She paused.

“Then the papers,” said Sir James slowly, “are still at the back of the picture in that room.”

“Yes.” The girl had sunk back on the sofa exhausted with the strain of the long story.