I indicated in what direction the mist had shrouded the other man, and he looked up at it for an instant. But he was down on the rank wet grass, filing at his iron like a madman, and not minding me or minding his own leg, which had an old chafe upon it and was bloody.
– Charles Dickens
Great Expectations, Chapter 3. One of the two escaped convicts Magwitch makes good use of the file Pip gave him to break free from the iron cuff around his ankle. A simile compares him to a madman as he saws frantically through the iron. The scene occurs on the marshes, a symbolic setting in the novel indicating uncertainty and concealment.