The Year of the Revolution II. The Discovery of Friendship

How a single act of a single person can determine those of an entire generation.
What would have become of the fate of Severus Snape, of Hogwarts', of the entire Wizarding World's, if he had decided to make a simple timid gesture in a direction that no one suspected could have such consequences?
This story is part of a series, but the first part can be read independently of the rest.