One thing that puzzles them for the first little while is why they haven't run across any other ghost aside from each other? Where has everybody else gone? Then they meet an elderly man who is able to remember them from previous meetings. Curious as to why he has this capability they investigate and discover that he only has a short time left to live. As they get to know him they discover he has been keeping a secret from his wife. Finally, just before he dies he tells her and he dies happy. Maeve and Mark see him just after he dies, and he thanks them for giving him the courage to talk to his wife. However, the second they turn their backs on the old man he disappears, and they never see him again.
Now that they understand the only reason they're hanging around is because they have unfinished business to take care of most series of this sort would have Maeve and Mark happily fade away into some sort of eternal bliss by miraculously finding a way to deal with their own unfinished business. However, the writers of Shades haven't been doing the expected, i.e. read sentimental, route throughout, and they don't start now. Just because someone's dead doesn't make them any more insightful then they were when they were alive. I'm not going to spoil the ending of the series for you by telling you how its resolved. However, I will say that it stays true to the way the story has been told all along and it makes perfect sense considering the characters and the plot.
Whether you believe in ghosts or don't, Shades is a beautifully told story about two people thrown together under very peculiar circumstances learning to make the best of it. Well acted and intelligently written, it tackles the subject of death and survival with humour and sympathy without once stooping to cheap sentimentality. Whether seen through the eyes of the two central characters or through those they've left behind, the series never strikes a wrong note. It may not be exactly what happens after we die, but its definitely one of the more interesting takes on the subject you'll see in a long time.