Can you help with my novel idea?

Heres the Plot so far: A boy called Ash wakes up remembering nothing about his life. He is in the middle of an apocalyptic city where plants and undergrowth have taken over the skyscrs. He thinks he is the last person on Earth because he can't see anyone. Later in the story, he finds out he is actually dead and he can't see anything living but he can see everything dead. He finds others who know more about this "being dead" business and tries to find out about how he died. At the end of the story he finds out he was being used to smuggle drugs for a criminal organisation and he jumped off a building to escape his problems. How am I going to end the story? I don't want to end it with an entirely happy ending, but more of a cliffhanger. Please make it better than " and I woke up and it was all a dream. Thanx!