Booth searches in his past because dead bodies start appearing close to Washington, D.C. that are connected to his old army unit. Brennan panics about her father, she doesn't know whether she can trust him, because of a medical procedure.
When a series of corpses with ties to Booth's former Army unit appear around D.C., Booth must dive into his past to find the killer before the killer finds Booth. Meanwhile, Brennan's father, Max, hides a serious medical procedure from Brennan, leaving her to grapple with her father's trust and mortality, as well as her family being in danger.
Booth goes after the vindictive Serbian fiend from his sniper past who killed his padre and targets veterans, notably himself. But he chooses to attack Booth's family, where Bones's terminal father, unwilling to let her impose 'logical' therapy, steps up as heroic grandfather.—KGF Vissers