Kagari has regained her childhood memories, but the last 12 years of her life are still shrouded in mystery. When forces unknown mobilize behind the scenes, Okabe investigates Kagari's past, while Suzuha fights to save the future from World War III. Science, subterfuge, and suffering culminate beyond anything Okabe could have foreseen on this perilous, uncharted path to Steins Gate.