Del is moving up.
One of the problems with life in the asteroid belt, though, is that "up" depends a lot on your point of view.
She's built a good life for herself out here, balancing her job as an Enforcer of what passes for the Belt's laws, with her extra activities that the rest of the Enforcers can never find out about.
But when the voices that plagued her childhood come back, she fails to prevent a terrorist attack, and her best friend is assigned to the investigation, all her secrets threaten to come out and her good life begins to unravel.