A middle-aged man named Richard is taking a train from New York to Boston with an old friend. He reveals that a few weeks prior, the sister of the old friend had called him wanting to meet up in New York to ask about her brother. This had happened in the past with either the sister, Carol Bannon, or the mother, Marie, asking for help locating Richard's friend Mark. Carol is a politician, as was her father, and she needs Mark's help because she is not doing well. Carol asks Richard to help find Mark, and even though Mark died years prior, Richard is not confused, and he takes the check that Carol offers.
First, Richard goes to New York, where he seeks out a man named Frank Parnelli. Frank knows that Richard is looking for Mark, and tells a story of when he met Mark. Frank was approached by Mark when he was in a bar who wanted $10 for a gun he had. Frank gave him $5. Frank suddenly felt different, like he had a purpose, and he robbed a department store with the gun and got thousands of dollars. As he was walking down the street after, he saw Mark, who then looked like the life had been sucked out of him. Frank used the money to go to L.A., and he soon realized that he was not alone in his head; Mark was in there too. Mark and Frank got involved with a woman named Red Ruby for a few years, until Mark got tired of being Frank and left his head. Frank tells Richard that one other person had come to him asking about Mark recently, and Richard knows it must be Desmond Eliot.
Richard recalls an instance when he and Mark were young, when a small child fell through broken ice when they were all skating. Richard had rescued the boy with Mark without wanting to, and he had not had control of his limbs. Richard goes to find Desmond Eliot, who tells him that after Mark had died, he had seen a Russian art dealer named Svetlanov, who had had the same intense look in his eyes as Mark. Eliot says that Mark's consciousness must have been elsewhere when Svetlanov died, and Richard thinks that he knows too much. Eliot tells Richard to find Ruth Vega.
Richard recalls when Mark died. He had been unwell for weeks prior, and had told Richard that his angel had left and was not coming back. Mark was not the same, and was scared and could barely function. He then died of an overdose. A few days after meeting with Eliot, Richard flies to Quebec to find Ruth. Ruth tells him that she and Mark were in love for a time. She and her grandmother have supernatural abilities, and they are able to tell parts of the future. Ruth tells Richard that Mark is looking for him.
Richard returns to New York City, and after a few days he sees a hip-hop star who has Mark's eyes. The hip-hopper's eyes widen, and then he slumps over, and Mark is in Richard's head. Mark reveals that each time he left his body it was harder to go back. Mark and Richard, as one entity, take the train from New York to go to Mark's childhood home in Boston, where Carol greets them at the door. Mark leaves Richard's head, and he feels empty.