In the novel, the protagonist navigates a labyrinth of secrets, hoping to uncover the truth about her father’s disappearance. One evening, she stumbles upon an old photograph hidden in the attic, which shows a young boy standing beside a crumbling statue. The photograph is labeled, 'Ben, keeper of the memories.' As she examines the image, she feels an inexplicable connection to the boy, as if he were a harbinger of the past. The next day, she recalls the word 'harbinger' and wonders about its meaning in the context of her discovery.

What does the word 'harbinger' most likely mean in this context?