As Donnelly escorts Carter and Reese to their incarceration, they are ambushed, their attacker who kills Donnelly and abducts Reese. That attacker is Reese's old and supposedly deceased ex-partner, Kara Stanton. Reese is not the first old colleague who she has abducted, the other being their old boss, Mark Snow. She has bombs strapped to their chests, and places them on a collective task, which she monitors remotely, and threatens to blow them up if they don't comply. They have to figure out her motives to uncover what her mission is. Meanwhile, Donnelly's death places Carter in an emotional conundrum of self-preservation versus leaving the scene of a crime. Finch convinces her that she needs to leave the scene, so that they plus Fusco can try to find Reese to save him before Kara completes her task and/or before she kills Reese.