Shut in a closet lit only by a high air vent through which a sunbeam enters at a certain hour, the narrator of The Plotinus has no place to lie down. This nameless “incarcerate,” barely covered in a sack and provided with an occasional pair of socks, endures conditions of abjection and torment that recall those of the prisoners in Abu Ghraib. Hoping that someone out there might decipher his “desperate rappings,” he taps out his story in code on the air vent (he “knuckles” it). Flashes of stoical humor bring him close to the protagonist of Kafka’s “The Burrow,” or to Winnie in her pile of sand in Beckett’s Happy Days and Hamm and Clov in Endgame; his voice, formal and restrained, is a rueful witness to the inhumanity of the future that is upon us. The Plotinus is a novella, Rikki Ducornet’s fifteenth work of fiction, if collections of short stories are included. Published last year—the year she turned eighty—it is a succinct parable of lockdown and turns that recent worldwide experience into …