He said one day,
'If I'd any luck, I'd marry her and she'd die in about a year and leave me all the boodle.'
And then a queer startled look came into his eyes.
That was when he first thought of it...
"He talked about it a good deal, one way and another - about how convenient it would be if Linnet died.
I said it was an awful idea, and then he shut up about it.
Then, one day, I found him reading up all about arsenic.
I taxed him with it then, and he laughed and said:
'Nothing venture, nothing have!
It's about the only time in my life I shall be near to touching a fat lot of money.'
"After a bit I saw that he'd made up his mind.
And I was terrified - simply terrified.
Because, you see, I realized that he'd never pull it off.
He's so childishly simple.
He'd have no kind of subtlety about it - and he's got no imagination.
He would probably have just bunged arsenic into her and assumed the doctor would say she'd died of gastritis.
He always thought things would go right.
"So I had to come into it, too, to look after him."
She said it very simply but in complete good faith.
Poirot had no doubt whatever that her motive had been exactly what she said it was.
She herself had not coveted Linnet Ridgeway's money, but she had loved Simon Doyle, had loved him beyond reason and beyond rectitude and beyond pity.
"I thought and I thought - trying to work out a plan.
It seemed to me that the basis of the idea ought to be a kind of two-handed alibi.
You know - if Simon and I could somehow or other give evidence against each other, but actually that evidence would clear us of everything.
It would be easy enough for me to pretend to hate Simon.
It was quite a likely thing to happen under the circumstances.
Then, if Linnet was killed, I should probably be suspected, so it would be better if I was suspected right away.
We worked out details little by little.
I wanted it to be so that, if anything went wrong, they'd get me and not Simon. But Simon was worried about me.
"The only thing I was glad about was that I hadn't got to do it.
I simply couldn't have!
Not go along in cold blood and kill her when she was asleep!
You see, I hadn't forgiven her - I think I could have killed her face to face, but not the other way...
"We worked everything out carefully. Even then, Simon went and wrote a J in blood, which was a silly melodramatic thing to do.
It's just the sort of thing he would think of!
But it went off all right."
Poirot nodded.
"Yes. It was not your fault that Louise Bourget could not sleep that night... And afterward, Mademoiselle?"
She met his eyes squarely.
"Yes," she said, "it's rather horrible, isn't it?
I can't believe that I did that!
I know now what you meant by opening your heart to evil... You know pretty well how it happened.
Louise made it clear to Simon that she knew.
Simon got you to bring me to him.
As soon as we were alone together he told me what had happened. He told me what I'd got to do.
I wasn't even horrified. I was so afraid - so deadly afraid...
That's what murder does to you.
Simon and I were safe - quite safe - except for this miserable blackmailing French girl.
I took her all the money we could get hold of.
I pretended to grovel. And then, when she was counting the money, I - did it!