Spoiler Alert - Click to Toggle
In the novel by Susan Hill, Arthur is not a widower, Stella is his fiancé. He goes to Marsh House to try to clean up affairs, and thereby runs afoul of the Woman in Black, who really really enjoys being vindictive. Since he does not have any children to kill, she tries instead to drown his dog in quicksand. Arthur is able to rescue it, however, and as they lie gasping for breath, he sees the ghost glaring at him for spoiling her fun.
Years later, Arthur and Stella are married with a young son. They visit a fair where horse and buggy rides are offered. Stella takes the boy for a ride while Arthur strolls. Suddenly, he sees the Woman in Black staring at him from a under a tree. Horrified, he tries to stop the horse, but the ghost runs out in front of it and spooks it, causing it to rear up and dash the buggy against a tree, killing the boy instantly. Stella is mortally wounded and dies later. The end.