Herbert had sometimes said to me that he found it pleasant to stand at one of our windows after dark, when the tide was running down, and to think that it was flowing, with everything it bore, towards Clara. But I thought with dread that it was flowing towards Magwitch, and that any black mark on its surface might be his pursuers, going swiftly, silently, and surely, to take him.
– Charles Dickens
Great Expectations, Chapter 46. Pip is fearful for the safety of Magwitch the convict who is in hiding in Clara’s house and is being pursued by Compeyson. Having spent time with the convict, Pip has grown close to him but realizes the risk he has taken to return to London to see Pip. In the symbolism of the tide, Herbert sees it flowing towards his love Clara, but to Pip it is ominously moving towards Magwitch and his capture.