This episode moves the story and Athena quite a bit forward and with some rather intriguing encounters. While there is still interaction with the Xiiginn, most of that happens late in the story. Most of the novel focuses on the Boxen and Athena crew looking for safe-harbor and the Boxen and previous commander of the Athena attempting to escape Pluto before the Xiiginn finds them.
There are plenty of close-calls and some role-reversal plot twists that continue to make for an entertaining novel, all the more so due to Heff Hays superb narration skills.
Onto book 5, Rising Force.