Reading "The Return of Chorb," one might be tempted to ask, "Chorb, what the heck are you doing?" It’s a fair enough question. The guy has just buried his wife in the south of France but left before the funeral. He hasn’t told her parents and instead pretended she was ill. He’s now attempting some sort of macabre reincarnation by retracing his steps and re-living the past, right down to his sex-less wedding night. Oh, and after he sees a ghost and flips out screaming, he sits around smiling. We’ve got a lot of "Why?" questions to address here. Fortunately, most of the answers are right there in your text.
Let’s start with why Chorb doesn’t tell the Kellers. The text says: "he wished to possess his grief all by himself, without tainting it by any foreign substance and without sharing it with any other soul. […] nothing, it seemed to him could be purer than such a death." Now compare this to Chorb and his wife’s actions on their wedding night. Rather than share their joy with others at the wedding reception, they chose to keep it for themselves – pure and untainted. Then you’ve got the actual nighttime activities – a kiss on the neck rather than sex. Again, pure and untainted. Chorb’s actions after his wife’s death, then, are entirely consistent with his actions while she was still alive. This is the nature of his love for her: something that exists only between them. Her death, as well, belongs only to Chorb, not to the rest of the world.
OK, so why does Chorb reenact the past like this? Does he want to bring his wife back, or is he scared of her ghost? Again, we have to go to the text. "He thought that if he managed to gather all the little things they had noticed together—if he recreated thus the near past—her image would grow immortal and replace her forever." Chorb doesn’t want to bring back the ghost of his dead wife – he wants to create in his mind a safe, everlasting memory of her. Once he’s done that, he can stop imagining her ghost. Check out the next line: "Nighttime, though, was unendurable. Night imbued with sudden terror her irrational presence." Again, he’s scared of the ghostly image of his dead wife, so he wants to replace it with the memory of her when she was alive.
To do so, however, Chorb has to face his demons, so to speak. As he has traveled backwards from the south of France, re-tracing his steps, he has also traveled backwards in time. By the time we join the story, he’s gone all the way back to Germany, and all the way back to his wedding night. He’s been re-living every moment, and this is the final step in his test. Again, go to your text to understand this: "Chorb traveled back to the very source of his recollections, an agonizing and yet blissful test now drawing to a close. All there remained was but a single night to be spent in that first chamber of their marriage, and by tomorrow the test would be passed and her image made perfect."
But why the prostitute? It could be that Chorb was simply too scared to sit around in that creepy hotel room, with the "naked bulb" swinging from the ceiling and the moth pinging against the lamp. The text suggests this: "Chorb suddenly understood that […] he would not be able to sleep alone in that room." On the other hand, using a woman to re-create his wife seems like the final obstacle in Chorb’s quest. That’s why the "test" isn’t over until Chorb wakes up, screaming, thinking that he’s seen his wife. It’s almost as though he has to undergo that terror to be complete, to put her ghost to rest and "replace" it with a new "image." And that’s why Chorb is smiling at the end of the night – because "he realized the ordeal was over." Not just the screaming, ghost-seeing ordeal, but the quest he began way back in the south of France. It’s finally done. And so are we.