In the year 2420, war looms between the galaxy's two most powerful empires: the tyrannical Theocracy and the protectionist Commonwealth. Caught in the middle sits the occupied outpost system Cadiz, where young officer and aristocrat Katherine "Kat" Falcone finds herself prematurely promoted at the behest of her powerful father. Against her own wishes, Kat is sent to command the Commonwealth navy's newest warship, Lightning.

Determined to prove she has value beyond her family name, Kat struggles to earn her crew's respect and find her footing as the youngest captain in naval history. She soon discovers the situation on Cadiz is even worse than anyone in power anticipated. War isn't just a possibility - it is imminent. Yet the admiral in position to bolster defenses refuses to prepare for a fight. Can Kat find a way to investigate the enemy, alert the Commonwealth, and whip an entire fleet into fighting shape before the Theocracy's war machine destroys everything she holds dear?