Low on fuel and hunted by the Fleet of Knives, the sentient warship Trouble Dog follows a series of clues that lead her to the Intrusion - an area of space where reality itself becomes unstable. But with human civilization crumbling, what difference can one battered old ship have against an invincible armada?

Meanwhile, Cordelia Pa and her step-brother eke out their existence salvaging artifacts from an alien city. But when Cordelia starts hearing the city's song in her head, strange things start happening around her. What extraordinary affinity does she have for this abandoned technology, and how can it possibly help the Trouble Dog?