Symbolism, Imagery, Allegory
At first the shadow of the Marshalsea is a real thing: the high walls of the prison block most light from coming into the little yard. But soon, the idea of a Marshalsea shadow falling on someone comes to mean the long-term effects of having been a prisoner there. Whenever Dorrit starts to really act up, Amy thinks she can see the shadow of the wall on him. Even more sadly, when Amy has a hard time adjusting to the rich lifestyle the Dorrits lead in the second half of the novel, she says she herself can never get out from under that shadow. It's a strong and moving image – easy to imagine visually and so full of rich meanings. Think about it – what kind of things do we usually associate with shadows? Are there positive meanings as well as negative ones? Who else does the Marshalsea shadow touch?