The massacre of Sahmot is underway. The town's fleet is in ruins. Horizon is barely functional but racing for home nonetheless, and Starlight is her closest ally-two hours behind her sister ship. Oren prays to his Ancestors for a miracle or mercy, but when they finally reach his home, they are met with an incomprehensible tragedy. The face of the quadrant irrevocably changes in a single moment. As the reeling survivors grieve and struggle to regroup and retaliate, Rin Cooper realizes what Matzepo meant when she warned her, "Do not lose the horizon line." Her grief is drowned by a rage that rivals her father's, and now more than ever, she is sure she was put in this universe to kill Jon Bledsoe. But every action has an equal and opposite reaction, and as Rin and her family brutally learn, the cost of bravery is steep.