[1][2][3] Chronologically, Once a Hero directly follows Winning Colors, even overlapping partially, but the focus distinctly shifts to young Esmay Suiza, who came to prominence after successfully leading a mutiny against her traitorous captain and intervening to decisive effect in the Battle of Xavier (as Winning Colors records).

Thorough and complete, neither the Board of Inquiry nor the court-martial find Suiza guilty of anything, and so she is allowed to take a vacation before her next assignment.

While talking with an old soldier who had served under her father (one of the four highest military commanders on Altiplano) and was a family friend, she learns that the nightmares and her dislike of command and horses were psychological trauma from when, as a child, she had ventured into a warzone seeking her father.

Meanwhile, some mendacious and greedy civilian contractors for the Fleet have agreed to carry out a job for the barbarian space-warriors of the Bloodhorde: they would take a Fleet contract to rekey the command sequences of various missiles, and when they were aboard the specified massive Deep Space Repair vessel, covertly disable its self-destruct mechanism.

After catching a resupply vehicle to the Kos, Suiza is assigned to a Major Pitak in Hulls and Architecture; Pitak immediately begins running Esmay ragged with errands and learning everything she needs to know about spaceship structural design and how to repair and fix vessels.

As the months pass by Suiza settles in; so do the traitorous civilian contractors who productively improve the hours by disabling the self-destruct without tripping the monitors.

Suiza is sent by Major Pitak to take pictures of the forward section of the hull to ascertain the full extent of the damage.

Suiza discovers instead the first prong of the Bloodhorde plan: a massive mine was planted on Wraith, programmed to wait until Wraith was brought into one of the Kos's repair bays and then detonate; this would incapacitate the Kos and make it easy meat for the waiting Bloodhorde assault group.

After making inquiries as to their location (most had vanished), whether they were injured at all like they should have been, and whether any senior Wraith officers recognize them, it is concluded that Kos has been boarded by Bloodhorde commandos seeking to capture the DSR and massively upgrade the Bloodhorde's industrial infrastructure and especially its military construction capability, greatly increasing its killing power.

They escape the cabin with the injured captain and link up with some personnel who had made it to the security lockers before the Bloodhorde.