"I dreamed of a girl named Martha once," Charles would say. "Maybe if I would have looked, I would have found her."
And then it would be bedtime. Or perhaps Mark would want more conversation. "What do you think of girls?" he would ask again, and the discussion would follow its same course.
Charles grew old. His limbs lost their flexibility, and some of his wiring started to corrode. Mark would spend hours keeping the robot in repair.
"You're getting rusty," he would cackle.
"You're not so young yourself," Charles would reply. He had an answer for almost everything. Nothing involved, but an answer.
It was always night on Martha, but Mark broke up his time into mornings, afternoons and evenings. Their life followed a simple routine. Breakfast, from vegetables and Mark's canned store. Then the robot would work in the fields, and the plants grew used to his touch. Mark would repair the pump, check the water supply, and straighten up the immaculate shack. Lunch, and the robot's chores were usually finished.
The two would sit on the packing case and watch the stars. They would talk until supper, and sometimes late into the endless night.
In time, Mark built more complicated conversations into Charles. He couldn't give the robot free choice, of course, but he managed a pretty close approximation of it. Slowly, Charles' personality emerged. But it was strikingly different from Mark's.