“I don’t consider,” she said, in a slow, aggravating way, “that Ivor Dundas has behaved very well to—­to our family.  But I want you to understand this, Di.  If he is to be got out of this danger—­no doubt it’s real danger—­in any such way as you propose, it’s for me to do it, not you.  He’ll have to owe his gratitude to me.  And there’s something else I can do for him, perhaps—­I, and only I. A thing of value was stolen from him, it seems, a thing he was anxious to get back at any price—­even the price of looking for it on a dead man’s body.  Well, I think I know what that thing was—­I think I have it.”

“What do you mean?” I asked, astonished at her and at her manner—­and her words.

“I’m not going to tell you what I mean.  Only I’m sure of what I’m saying—­at least, that the thing is valuable, worth risking a great deal for.  I learned that from experts this morning, while you and your aunt were thinking about hats.”

For an instant I was completely bewildered.  Then, suddenly, a strange idea sprang into my mind: 

“That brocade bag you picked up in the Rue d’Hollande last night!”

It was the first time I had thought of it from that moment to this—­there had been so many other things which seemed more important.

Lisa looked annoyed.  I think she had counted on my not remembering, or not connecting her hints with the thing she had found in the street, and that she had wanted to tantalise me.

“I won’t say whether I mean the brocade bag or not, and whether, if I do, that I believe Ivor dropped it, or whether there was another man mixed up in the case—­perhaps the real murderer.  If I do decide to tell what I know and what I suspect, it won’t be to you—­unless for a very particular reason—­and it won’t be yet awhile.”

I’m afraid that I almost hated her for a moment, she seemed so cold, so calculating and sly.  I couldn’t bear to think that she was my step-sister, and I was glad that, at least, not a drop of the same blood ran in our veins.

“If you choose to keep silent for some purpose of your own,” I broke out, “you can’t prevent me from telling the whole story, as I know it—­how I went out with you, and all that.”

“I can’t prevent you from doing it, but I can advise you not to—­for Ivor’s sake,” she answered.

“For his sake?”

“Yes, and for your own, too, if you care for his opinion of you at all.  For his sake, because neither of us knows when he came out of Maxine de Renzie’s house.  You would go away, though I wanted to stay and watch.  He may not have been there more than five minutes for all we can tell to the contrary, in which case he would still have had time to go straight off to the Rue de la Fille Sauvage and kill that man, in accordance with the doctors’ statements about the death.  For your sake, because if he knows that you tracked him to Maxine de Renzie’s house, he won’t respect you very much; and because he would probably be furious with you, unable to forgive you as long as he lived, for injuring the reputation of the woman he’s risked so much to save.  He’d believe you did it out of spiteful jealousy against her.”