The population of Quirni want Erica and Matilda Kinsley dead, even after the Quirni Delegate reveals why Matilda was judged innocent. To be safe on Quirni, Erica must prove Matilda's innocence beyond any doubt. The best way to do that is to find the real killer. She knows how it can be done, but her means are illegal. 

Convincing Claimant Mois proves difficult, but he knows as well as anyone that the Delegate Faction working against them. Quirni is supported by off-world interests, and it becomes stronger every day. Breaking Quirni law could put Erica in jail, but she prefers that to the Faction becoming stronger. The man she loves is her guard and a loyal agent, Captain James Kennedy. If the Faction has enough time to gather resources, they will eventually overpower the loyal agents. It wouldn't matter how outgunned or out manned James' unit becomes, they would give their lives to save Erica, Matilda, or a claimant. 

Unknown to Erica, James loves her as much as she loves him. He can't admit his feelings until his job as her guard is done. That won't happen until the Faction is destroyed, but the Faction members hide in the ranks of loyal agents. No one has figured out a way to identify them. James realizes they can use Erica. Her personality is broken by dissociation disorder, and one part of her loves Samuel Kinsley enough that she would do anything for him. Samuel could lead them to the rest of the Faction, but James hesitates to do it. Not only does it put Erica in her father's hands, a man she hates, but using Sal might submerge Erica permanently and destroy the woman James loves. It could save her life, but risk her sanity and their chance at a future together. Unknown to him, it might also interfere with the one chance they all have to prove the truth about Erica's investigation of Quirni's computers. 

Nigh is the second audiobook in the Quirni Series.