Commander Sheperd is back from being dead for two years. In that time a new planet, Ungula, has discovered and joined Citadel Space. The only problem is that their technology doesn't make a lick of sense, they've got one ambassador to represent about a dozen different sentient species, and to top it all off that ambassador seems to be insane even by their own standards.
So naturally Princess Twilight will be joining Sheperd's crew. After all, she's done the "save everything" deal once or twice over the centuries. She has experience. Now she just has to figure out how to ditch being an ambassador. Maybe if he kidnapped her...