Ahh, you may have missed the part about Tess Woods, the owner of Afterlife Antiques, who also seems to share a past with Marcus. These people with ties back to the Twenties seem like ghosts returned from the past. As Salman Rushdie says,“Now I know what a ghost is. Unfinished business, that's what.” Well, there's a lot of unfinished business in Marcus' life and it doesn't just simply link back to the parts of his own life affected by memory loss - there's an element of Jung's psychology here about the Collective Unconscious of mankind and the way we carry around our ancestors inside us - why? To fulfill their lives? I don't know.