In Batman Begins, Scarecrow releases the Fear toxin into the Narrows. We see a bit of chaos, but we don't find out what happened in full. It seems like a lot of people must have been killed. Is there more information about the events off screen and after the movie ended?
This is covered in the film's official novelisation. There was a riot in the Narrows and several hundred people were killed. After the cure was found, the area returned to a semblance of normality:
In the week since the monorail incident and the massive disruption of the city’s infrastructure, Gordon and his cops had restored order and the public works guys had completed the most necessary repairs to the water system. Pretty soon, everyone who wanted one would have an injection of the serum Rachel Dawes had given him and the nutso stuff Crane and Rā’s al Ghūl had put into the air wouldn’t ever again be a threat. Every drug lab in the state was helping turn out batches of the serum and most of the severely damaged citizens had already been injected and were returning to their sane selves. Those who had been under the influence of Crane’s hallucinogen the longest would need years of therapy, but there were only small numbers of those. There were also a couple of hundred people dead, but nothing could be done about them except to mourn. Even the Narrows area was returning to normal, or at least as “normal” as the Narrows ever got. Gordon had never exactly been a Mr. Sunshine, but he felt cautiously optimistic. Maybe things were looking up.