Mrs Verloc's mental condition had the merit of simplicity; but it was not sound.

It was governed too much by a fixed idea.

Every nook and cranny of her brain was filled with the thought that this man, with whom she had lived without distaste for seven years, had taken the "poor boy" away from her in order to kill him--the man to whom she had grown accustomed in body and mind; the man whom she had trusted, took the boy away to kill him! In its form, in its substance, in its effect, which was universal, altering even the aspect of inanimate things, it was a thought to sit still and marvel at for ever and ever.
Mrs Verloc sat still.

And across that thought (not across the kitchen) the form of Mr Verloc went to and fro, familiarly in hat and overcoat, stamping with his boots upon her brain.

He was probably talking too; but Mrs Verloc's thought for the most part covered the voice.
Now and then, however, the voice would make itself heard.