Answer:
These were the events that fatally heated-up the slavery debate.
The Scott decision (the Supreme Court ruling that slavery was protected by the Constitution) delighted the South as much as it inflamed the Abolitionists.
Harpers Ferry convinced the South that the Abolitionists were planning to distribute arms to the slaves to provoke a nationwide rebellion.
Lincoln's election meant that there would be no more slave-states, so the South would always be out-voted in Congress, which would pass laws unfavourable to Southern interests.
There was going to be war.