Clouds of Witness continued

He said, would I 'scuse him for interferin' in a very delicate matter, and all that, but did I know who Cathcart was? Said he'd met him in Paris during the war, and he lived by cheatin' at cards—said he could swear to it, with details of a row there'd been in some French place or other. Said he knew I'd want to chaw his head off—Freeborn's, I mean—for buttin' in, but he'd seen the man's photo in the paper, an' he thought I ought to know.”
The upper classes, particularly in England, played cards as a devoted hobby, from poker to bridge to whist. Someone who was caught cheating at cards was no longer considered a gentleman.
The Coroner: “Did this letter surprise you?”
Duke of D.: “Couldn't believe it at first. If it hadn't been old Tom Freeborn I'd have put the thing in the fire straight off, and, even as it was, I didn't quite know what to think. I mean, it wasn't as if it had happened in England, you know. I mean to say, Frenchmen get so excited about nothing. Only there was Freeborn, and he isn't the kind of man that makes mistakes.”
The Coroner: “What did you do?”
Duke of D.: “Well, the more I looked at it the less I liked it, you know. Still, I couldn't quite leave it like that, so I thought the best way was to go straight to Cathcart. They'd all gone up while I was sittin' thinking about it, so I went up and knocked at Cathcart's door. He said, 'What's that?' or 'Who the devil's that?' or somethin' of the sort, and I went in. 'Look here,' I said, 'can I just have a word with you?' 'Well, cut it short, then,' he said. I was surprised—he wasn't usually rude.
'Well,' I said, 'fact is, I've had a letter I don't much like the look of, and I thought the best thing to do was to bring it straight away to you an' have the whole thing cleared up. It's from a man—a very decent sort—old college friend, who says he's met you in Paris.' 'Paris!' he said, in a most uncommonly unpleasant way. 'Paris! What the hell do you want to come talkin' to me about Paris for?' 'Well,' I said, 'don't talk like that, because it's misleadin' under the circumstances.'
'What are you drivin' at?' says Cathcart. 'Spit it out and go to bed, for God's sake.' I said, 'Right oh! I will. It's a man called Freeborn, who says he knew you in Paris and that you made money cheatin' at cards.' I thought he'd break out at that, but all he said was, 'What about it?' 'What about it?' I said. 'Well, of course, it's not the sort of thing I'm goin' to believe like that, right bang-slap off, without any proofs.' Then he said a funny thing. He said, 'Beliefs don't matter—it's what one knows about people.' 'Do you mean to say you don't deny it?' I said. 'It's no good my denying it,' he said; 'you must make up your own mind. Nobody could disprove it.' And then he suddenly jumped up, nearly knocking the table over, and said, 'I don't care what you think or what you do, if you'll only get out. For God's sake leave me alone!' 'Look here,' I said, 'you needn't take it that way. I don't say I do believe it—in fact,' I said, 'I'm sure there must be some mistake; only, you bein' engaged to Mary,' I said, 'I couldn't just let it go at that without looking into it, could I?'
'Oh!' says Cathcart, 'if that's what's worrying you, it needn't. That's off.' I said, 'What?' He said, 'Our engagement.' 'Off?' I said. 'But I was talking to Mary about it only yesterday.' 'I haven't told her yet,' he said. 'Well,' I said, 'I think that's damned cool. Who the hell do you think you are, to come here and jilt my sister?'
To jilt is to deceive or drop (a lover) suddenly or callously. Possibly this is from the obsolete jilt, harlot, alteration of gillot, diminutive of gille, woman, girl, from Middle English.

Well, I said quite a lot, first and last. 'You can get out,' I said; 'I've no use for swine like you.' 'I will,' he said, and he pushed past me an' slammed downstairs and out of the front door, an' banged it after him.”
The Coroner: “What did you do?”