She guessed the Dowager's treacherous purpose.

And no sooner had she guessed it than, with a choking sob, she told herself that what madame could do that could she also.
Suddenly Garnache saw an opening; Fortunio's eyes, caught by the Dowager's movements, strayed for a moment past his opponent, and the thing would have been fatal to the captain but that in that moment, as Garnache was on the point of lunging, he felt himself caught from behind, his arms pinioned to his sides by a pair of slender ones that twined themselves about him, and over his shoulder, the breath of it fanning his hot cheek, came a vicious voice-- "Stab now, Fortunio!" The captain asked nothing better.

He raised his weary sword-arm and brought his point to the level of Garnache's breast, but in that instant its weight became leaden.

Imitating the Marquise, Valerie had been in time.

She seized Fortunio's half-lifted arm and flung all her weight upon it.
The captain cursed her horridly in a frenzy of fear, for he saw that did Garnache shake off the Marquise there would be an end of himself.