The unnamed narrator's unnamed wife used to work for a blind man named Robert. Robert's wife has recently died, and he's coming to visit the narrator and his wife. The narrator isn't happy about this. He thinks blind people are sad and depressing. He bases this assessment on what he's seen in movies. Apparently, his wife and Robert have been corresponding by audio tape for the past ten years. She met Robert in Seattle one summer before she got married to a man training to be an officer in the Navy. On her last day on the job she let Robert touch her face, then she wrote a poem about it. Much later showed it to the narrator when they began going out. He didn't like the poem.
After she'd been married to her officer, her "childhood sweetheart" (1.5), for about a year she contacted Robert and they began corresponding. She told him she wasn't happy with her life as an officer's wife. At one point she became so miserable she attempted suicide. She left her husband and got a divorce. Through all those years she sent Robert tapes and told him all about her life. And now he's coming to spend the night.
The narrator finds his wife in the kitchen making dinner before she leaves to pick up the Robert from the train. The narrator makes a joke about taking him bowling. This upsets her, and she reminds him, rather angrily, that Robert is probably grieving over the loss of his wife, Beulah. She tells him that if he doesn't try to make Robert comfortable, that means he doesn't love her. Then she tells him that Robert married Beulah after she came to work for him. They had a great marriage, but then Beulah got cancer and died. The narrator thinks it's incredibly sad that Beulah died without Robert ever seeing what she looked like. He thinks it must have been terrible for her to go through life without being seen by her husband.
When Robert arrives the narrator makes drinks for everybody and they all drink while Robert and the woman talk. Soon they have a big dinner and seem to enjoy eating together. After dinner there are more drinks and more conversation. When the woman goes up to change clothes, the narrator rolls two marijuana cigarettes and begins smoking them with Robert, who's never smoked marijuana before. When the woman returns she smokes a little bit too and then falls asleep on the couch between the two men.
The narrator is watching TV, and Robert is listening, in between seeming to fall asleep. The only thing on is a documentary about cathedrals. The narrator wonders if Robert has a good idea of what a cathedral is, and so he asks him. Robert asks him to try to describe a cathedral for him, because he can't picture one. The narrator tries, but he can't find the words to adequately describe what he sees. Robert gets a bright idea and tells the narrator to find paper and a pen. The narrator gathers the requested items and returns to Robert. They sit on the floor. Robert puts his hand on the narrator's hand (the one holding the pen) and tells the narrator to start drawing.
The narrator gets into it, and starts drawing the cathedral with Robert's hand on his. After a time Robert examines the drawing with his fingers, and tells the narrator he's on the right track. Then they resume. The woman wakes up and can't understand what they are doing, even though Robert tells her. Then Robert tells the narrator to close his eyes. He does, and he completes the drawing with his eyes closed. The experience feels amazing. Robert tells him to open his eyes, but he doesn't. The narrator doesn't feel like he's "inside anything" now, and he likes the feeling. And that's the end of "Cathedral."