And the heroic old woman resolved on going away from her children as an act of devotion and as a move of deep policy.
The "virtue" of this policy consisted in this (Mrs Verloc's mother was subtle in her way), that Stevie's moral claim would be strengthened.

The poor boy--a good, useful boy, if a little peculiar--had not a sufficient standing.

He had been taken over with his mother, somewhat in the same way as the furniture of the Belgravian mansion had been taken over, as if on the ground of belonging to her exclusively.

What will happen, she asked herself (for Mrs Verloc's mother was in a measure imaginative), when I die?
And when she asked herself that question it was with dread.
It was also terrible to think that she would not then have the means of knowing what happened to the poor boy.

But by making him over to his sister, by going thus away, she gave him the advantage of a directly dependent position.