We've discussed foreshadowing before but not overshadowing. Some works mention other characters who we never see, or who play a role behind the background and have an effect on the story or characters from afar - as if their devil-fingers creep over the landscape to exact actions upon the plot - muwahahaha! That character's presence is felt by the reader/audience.
Jim Crace, in The Pesthouse evokes a character who is no longer part of the story in a really interesting way that isn't really overshadowing in the above sense of working behind the scenes, but rather to relate us and the characters back to another character.
Franklin no longer knows where his elder brother, Jackson, is. They've been travelling toward the coast and become split up - it's okay, you won't hear any spoilers here. Franklin, the younger, occasionally referred to Jackson as "Mighty", and looked up to him as always being there, resolute and strong. Now that Jackson is gone, Franklin is becomming his own man, and after a small victory for himself, he relates back to Jackson - reminding us subtly of Jackson and that Jackson is on Franklin's mind:
His first step in the east. He should have felt proud of himself. Triumphant. Mightily relieved. He should have felt brave. But he did not. Rather, now that he no longer needed to be determined, he counted himself weak, dishonest, craven and troubled by disloyalty.
Note the reference to mightily. It is interesting that Crace then pulls that back by Franklin's anxieties about himself. He's achieved something that Jackson would have done without batting an eyelid, and then he is upset by it.
I wonder if we will feel Jackson's prescence as the story continues?