SINCE IT WAS Thomas Trumbull who was going to act as host for the Black Widowers that month, he did not, as was his wont, arrive at the last minute, gasping for his preprandial drink. There he was, having arrived in early dignity, conferring with Henry, that peerless waiter, on the details of the menu for the evening, and greeting each of the others as he arrived. Mario Gonzalo, who arrived last, took off his light overcoat with care, shook it gently, as though to remove the dust of the taxicab, and hung it up in the cloakroom. He came back, rubbing his hands, and said, "There's an autumn chill in the air. I think summer's over." "Good riddance," called out Emmanuel Rubin, from where he stood conversing with Geoffrey Avalon and James Drake. "I'm not complaining," called back Gonzalo. Then, to Trumbull, "Hasn't your guest arrived yet?" Trumbull said distinctly, as though tired of explaining, "I have not brought a guest." "Oh?" said Gonzalo, blankly. There was nothing absolutely irregular about that. The rules of the Black Widowers did not require a guest, although not to have one was most unusual. "Well, I guess that's all right." "It's more than all right," said Geoffrey Avalon, who had just drifted in their direction, gazing down from his straight - backed height of seventy - four inches. His thick graying eyebrows hunched over his eyes and he said, "At least that guarantees us