Good old Mother Nature plays a huge role in The Woman in Black. The crazy, murderous kind of mother, like Jennet. He may come from London, where everything is man-made and contained, but out in the countryside Arthur's on his own and left to the power of the elements. The bleak, powerful, indifferent elements. This might even be scarier than the ghost.
Despite all the modern technological advances in the story, such as the steam train and the telephone, the power and complexity of nature eventually wins out.
Nature dictates Arthur's entire trip at Eel Marsh House, even cutting him off from human society against his will.