Despite Misaka's tireless efforts and her explosive confrontation with ITEM at Academy City's Pathology Analysis Laboratory, progress on the "Sisters" cloning project hasn't missed a beat. Something big is behind the Sisters, and the deeper Misaka digs, the less she understands. Out of options, Misaka finally resorts to a deadly gambit against the project's crowing achievement: the Accelerator himself. In her darkest moment, an unlikely hero emerges who may turn out to be Misaka's only salvation.