What warning does Mr. Lawrence give Gilbert?

Mr. Lawrence warns Gilbert to stay away from his wife.

“What is the matter, Markham?” whispered he.

I replied by a wrathful and contemptuous stare.

“Are you angry because Mrs. Graham would not let you go home with her?” he asked, with a faint smile that nearly exasperated me beyond control.

But, swallowing down all fiercer answers, I merely demanded,—“What business is it of yours?”

“Why, none,” replied he with provoking quietness; “only,”—and he raised his eyes to my face, and spoke with unusual solemnity,—“only let me tell you, Markham, that if you have any designs in that quarter, they will certainly fail; and it grieves me to see you cherishing false hopes, and wasting your strength in useless efforts, for—”