In "The Boxcar Children Mysteries Box Set: Books One Through Twelve" by Gertrude Chandler Warner, a moment of suspense arises as the children are engaged in their activities. Their attention is captured when they hear the distinct sounds of a horse and cart approaching down the road. This unexpected arrival creates a mix of curiosity and anticipation among the children, hinting at potential adventures or encounters that await them.

The children's world is filled with mystery and exploration, and the sound of the horse and cart symbolizes a break in their routine. It represents the possibility of new experiences and interaction with the outside world, which is a central theme in their adventures. This moment serves as a reminder of the excitement that comes with the unknown as the story unfolds.