Toward the end of “Logan’s Run,” Michael York and Jenny Agutter, escaping from a future society that murders people when they turn 30, enter an ivy-strangled rotunda and are soon amazed. Hearing a noise in the ostensibly empty building, York reaches down and pries off the arm of a chair on the ground. Slowly, he approaches a parted door. A cat scurries out. Coming in closer, he finds something he’s never seen before: an old man. Dressed in ragged clothes, the man sits at a desk, cracking walnuts with a hammer. Or gavel — the Senate gavel. This feral-looking older gentleman made a home for himself, and his many cat companions, in the wreckage of the Capitol building.