Josie Powell was a former rival of Molly's. Bloom encounters her briefly in "Lestrygonians"' and tries to decide how she has aged. Josie's husband, Denis, is starting to lose his mind. Josie has to follow him around Dublin to keep track of him. Yesterday, he received a postcard with the letters U.P. on it, which he took to be some sort of offensive practical joke. Today, Josie follows him around as he tries to take legal action over the postcard, though all the lawyers turn him down. Bloom takes sympathy on Josie, but most of the men in Dublin seem to regard the couple themselves as a practical joke. In "Cyclops," Bergan laughs at Breen moving around out front and it seems as if Bergan was the one who sent him the postcard.
Early on in Bloom's dream sequence in "Circe," he imagines bumping into Josie Breen. The two of them flirt and remember the time when they were involved with one another. Bloom recalls how attractive Josie was and how sad it made him when she married Denis Breen. Just as Bloom is moving to the climax of his story however, Josie disappears.