Illusion of Control
The boss in the story, who is referred to only as "the boss," is a hard-working man who is clearly in control. For years, he had "slaved, denied himself" so that he could build up his business into something successful to leave behind for his son. He continued to work hard after his younger friend, Mr. Woodifield, had already retired and six years after his son had died. The irony is that despite his efforts to cling to control, he has none. There was nothing that he could have done to save his son.
Grasping for Grief
After Mr. Woodifield leaves, the boss asks his secretary not to be disturbed, and he "covered his face with his hands. He wanted, he intended, he had arranged to weep...." However, the tears do not come, and he is not overcome with grief for his son. He only feels something after he notices the fly in the inkwell and tortures it by rescuing it only to cover it with more ink until it dies. When the fly dies, the boss had "such a grinding feeling of wretchedness." The irony is that though he sat down expecting to weep for his son's mortality, he ends up feeling the sting of his own mortality. The incident with the fly further reinforces the idea that no amount of control -- such as the fly fighting to clean its wings of ink -- can prevent the inevitable end everyone must face.
When his son dies, the boss is overcome with grief. When he learns the news, he feels that his life is in ruins. However, time moves forward, and after his meeting with Mr. Woodifield, he finds that he is no longer even able to summon his grief. In fact, after the incident with the fly, "For the life of him he could not remember" what it was he had been thinking about previously. It is an ironic statement because it is "for the life of him" that he cannot remember his grief over his son's death. The boss's life is not in ruins but is still moving forward, and the thought of his own mortality is the only thing that shakes him now.
When Mr. Woodifield arrives at the boss's office, the boss feels sorry for him. He considers him a "frail old figure" and thinks "he's on his last pins." He behaves condescendingly toward Woodifield when he can't remember the story he wanted to tell about his daughters visiting the cemetery. The irony is that by the end of the story, the boss cannot remember thinking about his son's death only a few minutes earlier. He is also suffering the signs of his age.