The story foreshadows the boss’s complicated feelings about his son's death by briefly mentioning a photograph of the young man. As the boss proudly invites Mr. Woodifield to admire the many fancy things in his office, he deliberately fails to mention the photograph:
But he did not draw old Woodifield’s attention to the photograph over the table of a grave-looking boy in uniform standing in one of those spectral photographers’ parks with photographers’ storm-clouds behind him.
This passage appears on the very first page of the story, before readers know that the boss's son died in World War I. Even without this knowledge, though, it's easy to sense that the photograph holds some kind of deeper meaning for the boss, whose eagerness to ignore it suggests that there's something complicated about the way he thinks about his own son. After all, the boss is clearly a very proud man, so readers might expect him to boast extensively to Mr. Woodifield about his son. To the contrary, though, he tries to downplay the presence of the photograph, thus hinting that something has happened to make him avoid talking about his son altogether.
Furthermore, even the description of the photograph foreshadows the later revelation that the boss's son died in battle. He is described as a "grave-looking boy in uniform," a description that feels rather ominous, as the use of the word "grave" creates a serious atmosphere while also subtly gesturing toward death and burial. To that end, the "storm-clouds" looming behind the boss's son also lead to a somber, uneasy feeling, which is exactly what the boss seems to feel when he looks at the photograph. Although he has the photograph on prominent display, then, it's clear that it makes him uncomfortable, thus foreshadowing his inability—or unwillingness—to confront his own emotions about his son's death.