Now the demon, having bound Sha the Monk fast, neither came forward to slay him, nor beat him, nor even flung a single curse his way.

Sha Wujing is tied up on the floor and nothing whatever is being done to him, which is a good deal worse than something being done to him. 那怪 is the 黃袍怪, the Yellow-Robe Demon of the Moon-Waves Cave on Bowl-Son Mountain (碗子山波月洞) — husband to the stolen princess, and the enemy carried over from the chapters before. No killing, no beating, not one curse: that is not mercy. That is a man working something out.

He snatched up his steel sabre and mused within himself: "Tripitaka is a man of a superior realm, one sure to know the rites and their proprieties. Surely it cannot be that, having spared his life, I should find his disciples set on to seize me?"

And here is what he works out, with a bare blade in his hand. 綽 is chāo here, to snatch up a weapon (as in 綽刀), not the chuò of 綽約, "willowy, graceful." 上邦 is a "superior state," a realm further along in civilisation; the demon flatters 唐僧 as a man who must therefore keep 禮義 — ritual propriety and right conduct — and who could not possibly answer clemency with treachery. It is a gentleman's syllogism, delivered at knifepoint. In 又著他徒弟 the 著 that means "to set someone on to a thing" is zhuó.

Ah! — most likely my wife has sent some letter or other off to that kingdom of his, and the secret has leaked out.

One syllable, and the suspicion hardens into certainty. 噫 is that syllable. 渾家 is the homely everyday word for one's wife — nearer to "the missus" than to anything respectful. 走了風汛 says literally that the wind-signal has run off, and it is the set idiom for a secret getting out. Keep an ear open for it: the chapter uses it twice more, once when the princess coaches her husband on not leaking, and once when he leaks.

Let me go and put the question to her.

The vernacular 他 does no gendering at all — it serves for he, she and it alike — and here it means the princess. 問他一問, "put the question to her, just the once": four characters, not a threat among them, and every reader knows exactly what is coming.

And the demon, his savagery flaring up all at once, made ready to kill the princess.

陡起兇性 — his savage nature rearing up all at once — is the swerve from cold reasoning to murder. The princess is herself his captive, and she is the one who quietly let Tripitaka go. She is now first in line.