A ghost spoke to a painter and made him paint a portrait of her, so that she could go into the painting.
Before the ghost (presumably a priestess named Genuine) died, she had been sold into slavery. Long after she and her owner had died, the ghost of her owner had found the painter (Percy), and tried to buy his slave back.
There is also a possibility that Percy had fallen in love with Geniune's ghost, hence the refrain's lyrics. The portrait coming alive can be taken in several contexts: literally, as a dream, or as the ghost of Geniune possessing him.
Another possibility is that Genuine was a prostitute, although I'm not sure of that one.
Here is what I think:
A ghost spoke to a painter and made him paint a portrait of her, so that she could go into the painting.
Before the ghost (presumably a priestess named Genuine) died, she had been sold into slavery. Long after she and her owner had died, the ghost of her owner had found the painter (Percy), and tried to buy his slave back.
There is also a possibility that Percy had fallen in love with Geniune's ghost, hence the refrain's lyrics. The portrait coming alive can be taken in several contexts: literally, as a dream, or as the ghost of Geniune possessing him.
Another possibility is that Genuine was a prostitute, although I'm not sure of that one.