donât put anything in writing because letters can go astray or be stolen and cyphers can be decoded. But it also seems,â she finished crisply, âthat agents can be killed!â
âYes,â said Janet Rushton slowly. âAgents can be killed. That was why I didnât believe you when you came to my door tonight. I thought it was a trap. That you had come to kill me.â
âYou what! â
âWhy not? If anyone had told you a few hours ago that I was a Secret Service agent, would you have believed them?â
âWellâ¦â
âOf course you wouldnât! Because I donât look like your idea of a Secret Service agent.â
âYes, I suppose so. I see. No wonder you pulled a gun on me! I thought you must have gone mad; or else I had.â
âI know,â said Janet wearily. âI realized that if you werenât one ofâ them âthen I would have done something that was going to be appallingly difficult to explain away. But I had to do it, because the other risk was so much greater.â
âHow do you mean? What other risk?â
âIf you had been one of them and I had hesitated for fear you might not be, I should have had no second chance. It was better to risk letting myself in for a lot of awkward questions and complicated lying than to risk that. You see, itâs not just my own life thatâs at stake. Itâs far more important than that. Now that Mrs Matthews is dead Iâm the only person who knows what she knew. I was never any more than a sort of second string to her. She gave me all my orders. But now Iâm on my own and Iâve got to keep alive. Iâve got to! I canât let her down. I canât let it all be lost.â
The tired, passionate voice cracked queerly on the last word and after a moment Sarah said curiously: âWhat made you decide that I was on the level?â
Janet Rushton smiled wanly. âOh, partly intuition I suppose, but mostly simple arithmetic.â
âI donât understand.â
âDonât you? Itâs very easy. You hadnât any weapon on you and you had told me the truthâthere had been someone at the window: someone who must have been there quite a while, for they had made a very neat job of filing through that catch. Well, if you werenât on the level you wouldnât have warned me.â
âOh I donât know,â said Sarah with a smile. âI might have planted him there as a sort of decoy duck.â
âYes. I thought of that too. You learn to think of most things in this job. But that didnât add up either. If you had planted someone at that window you could only have done it to provide an alibi: an excuse for getting in or for getting me out, supposing I had refused to open the door to you. Your reasoning could have been that before letting you in I might run to the bathroom window and check up on whether you were speaking the truth, and then, convinced of your bona fides by a sight of the decoy duck, I would of course have opened the door.â
âThen what makes you thinkââ began Sarah.
âI didnât go to the window first,â interrupted Janet. âI made certain instead that you had no weapon on you; and by the time I got to the window, whoever had been there had heard us and gone. It did occur to me then that possibly it was a plot: not to kill me, but to gain my confidence. But if it had been that, then it was an entirely pointless gilding of the lily for your decoy to take on a long, cold and exceedingly tricky job on my window merely to provide an alibi, when the briefest demonstration would have served the same purpose equally well.â
âI see,â said Sarah slowly; and shivered. âYou seem to have it all worked out. Andâjust for the record of courseâI am on the level, you know.â
âI know,â said Janet, with an odd inflexion in her voice. She raised her