He knows and understands.

If he has had to leave me here alone, it is because it is necessary." "You have a great deal of faith in him," I remarked.
"He has always been kind to me," she answered, "and I know that the business upon which he is engaged just now is hazardous and difficult.

There are men who do not wish it to go through, and they watch for him.

If they knew his whereabouts they would try to stop him." "Felicia, do you know what that business is ?" I asked.
"I have some idea of it," she answered.
Her answer puzzled me.

If Felicia really had any idea as to the nature of it, and was content to play the part she was playing, it certainly could not be anything of an illicit nature.