She says it may excite him, and be very harmful.

What do you think about it ?" Jervis glanced at the invalid, who sat in a chair by the open door, gazing out at the evening sky, where the twilight still lingered.
'Duke Radford was sitting with his head stooped a little forward, and smiling placidly as if his thoughts pleased him.
"I don't think it would hurt him; he takes so little notice," the young man answered slowly.

Then he added: "But Miss Radford would know better about that than I do, and if she is afraid of the effect upon him, it would be well to be careful." "I don't think Katherine knows more about Father than I do, because you see she is not much with him, and I don't think he understands the difference between one person and another," said Mrs.Burton.
"He seems to find as much pleasure in talking to Oily Dave as to Astor M'Kree, and that is certainly different from what he used to be.

But it will be very hard if we have to shut nice people like the Selincourts out of the house just because it may upset Father, who probably won't even realize that they are strangers at all." "Well, we can but try him.

Let us see if the name brings any worry to him," said Jervis, and going across to the door he began to talk to the invalid.