Duarte's disciplined fleet captain leads the Barkeith toward Laconia, only to die with his crew at the gate in an incomprehensible transit event.
Sauveterre commands the Donnager-class battleship Barkeith and the Martian fleet that has quietly broken from Mars under Admiral Winston Duarte's authority. He treats the mission as an independent military initiative rather than a collapse of discipline, enforcing rigid standards on officers such as Lieutenant Babbage while the Free Navy's seizure of Medina traffic serves the larger plan. His professional contempt for the Belters is matched by confidence that their new power will only keep Earth and Mars distracted until Duarte is ready.
Sauveterre receives confirmation from Paolo Cortázar that the stolen protomolecule sample has reached the Laconian research effort and accepts organic modifications intended to let the Barkeith dock with an alien artifact. After Medina clears the fleet, he takes it through the Laconia gate with weapons ready. At the threshold, every human becomes a visible cloud of atoms, an alien presence moves through the spaces between matter, and Sauveterre recognizes the danger too late. He dies without registering the final moment.
A composed adult Martian naval captain in a meticulously straightened uniform, controlled and exacting in zero gravity, with a manner that makes duty and discipline feel like personal virtues.
Sauveterre is Duarte's reliable professional instrument, whose faith in military discipline carries a stolen fleet into a danger neither strategy nor force can control.