‘The Fly’ is a short story by Katherine Mansfield, and it delves into several themes and layers of meaning. Following are some of the main themes in the story:

Grief and Loss: The primary theme revolves around the profound grief and loss experienced by the boss. The story explores how grief can linger, affecting a person for an extended period, and how people often conceal their emotions. The boss's grief over his son's death, which occurred six years ago, is still fresh and vivid in his mind, highlighting the enduring impact of loss.

Emotional Repression: The boss's inability to express his emotions and cry is a central element of the story. He struggles to let his feelings out, choosing to focus on a trivial experiment with a fly as a means of coping with his inner turmoil. This theme highlights how individuals may suppress their emotions, particularly when dealing with grief and trauma.

Futility and Mortality: The experiment with the fly serves as a metaphor for the futility of human life and the inevitability of death. The boss's attempt to revive the dying fly symbolizes his desire to confront the impermanence of life. It also underscores the harsh reality that, in the face of death, human efforts are often futile, mirroring his feelings of helplessness regarding his son's death.

Memory and Time: The story plays with the concept of memory and time. The boss vividly recalls the past, particularly the day he received the telegram about his son's death. This highlights how certain memories can remain etched in one's mind, as if they happened just yesterday. The passage of time is explored in the context of grief, as the boss expected that it would ease his pain, yet it has not.

Isolation and Loneliness: The boss's solitude in his office is another prominent theme. He isolates himself from others, including his employees, and yearns for privacy to grapple with his emotions. His loneliness and the isolation he experiences are emblematic of the emotional distance that grief can create between individuals.

Resilience and Determination: On a more positive note, the story also touches on the themes of resilience and determination. The fly's efforts to clean itself after each ink drop demonstrate its unwavering spirit and courage, even in the face of adversity. This resilience contrasts with the boss's inability to move past his grief.

The Insignificance of Human Concerns: The story raises questions about the significance of human concerns and activities in the grand scheme of things. The boss's fixation on the fly and his experiment highlight the triviality of certain human endeavors when compared to the vastness of the universe and the inevitability of death.

In ‘The Fly,’ Katherine Mansfield masterfully weaves these themes together to create a poignant and thought-provoking narrative that explores the complex and enduring nature of grief, the human condition, and the intricacies of emotional expression.