What does Grampa say when Hiram confronts him about “being there”? chapters 16 - 17

After a considerable amount of trying to get Ralph to speak plainly, Ralph finally tells Hiram that he and his brother Ronnie saw Grampa with Milam and Bryant on the night Emmett was kidnapped. They also saw the men borrowing Grampa's truck after they bring Grampa back later in the evening. Hiram is shocked by this and he goes back into the house, and after a moment or two of thought, he confronts Grampa with this allegation. Grampa admits to this, but he insists that Milam and Bryant promised that Emmett would be alive as he had been when Grampa last saw him.