Symbolism, Imagery, Allegory
After its first appearance in "Lotus Eaters," the Gold Cup race pops up again and again. When Bloom runs into Bantam Lyons, he offers him his "throwaway" paper. Lyons thinks it is a tip on the race, though Bloom doesn't even realize that there is a horse named Throwaway involved. Well, as luck would have it, Throwaway comes out of nowhere and wins the race, beating out the horse that Blazes Boylan and Matt Lenehan bet on – Sceptre. The first sign of Boylan that Bloom sees when he returns home in "Ithaca" is Boylan's torn up betting tickets in the kitchen. Later, in "Penelope," we learn that Boylan was extremely upset about losing the race.
The use of the Gold Cup as an allegory for what happens in Ulysses is made explicit in "Cyclops." After Lenehan shares his mistaken belief that Bloom has placed a bet on Throwaway and won at five to one odds (which makes the narrator wonder why Bloom didn't buy them drinks), Joe Hynes says, "He's a bloody dark horse himself" (12.453). We wouldn't overdo the interpretation, but just as Throwaway is a dark horse, Bloom is not a very well-respected man in Dublin and today he happens to be wearing black for Dignam's funeral. The name Sceptre can't help but evoke all sorts of super-male phallic imagery, which makes it seem like Boylan corresponds to the favorite horse in the race. Yet Bloom, the dark horse, comes from behind and defeats him. The fact that Molly's last thoughts in the novel are for her husband instead of for Boylan might be taken to suggest that Bloom still holds the highest place in her heart.