This book takes place at the time of the episode in which G'Kar was in a cell at the Imperial Palace, and he and Londo had devised an agreement where the freedom of the Narns was a definite probability.
The only thing is, G'Kar had to stay and be beaten without mercy by Cartagia and his guards.
In this novel, things are complicated tremendously by a group of five Narn who have come to Centauri Prime to free G'Kar, not knowing that doing so would destroy the Londo-G'Kar arrangement for Narn freedom. To complicate this further, Franklin, Ivanova and Garibaldi are going to Narn to try to free G'Kar themselves.
Humor is added in another theme, this one involving Vir and Lyndisty, the woman he's engaged to, even though she hates Narns.
Actually, there's even another theme involved, this one with Serididan and Delenn who end up in the middle of a weapons-smuggling gang. So, there's quite a bit of goings on in the story, and it's pretty well done. It's all stuff that could have happened within the canon of the series, but just never mentioned.