Act 1

introduce the protagonist, the opposition character and the setting

Buck's initial situation

the situation that exists before the main action begins

The story's kickoff

the actions and situations that cause the main action of the plot to begin.

story objectives lead the protagonist to adopt a concrete goal

When the protagonist has a concrete goal then the story is in its Second Act.

Most often it is some action of the opposition character that forces the protagonist to form a concrete goal.

The opposition character is not necessarily recognized as the opposition character by the readers or the protagonist at this point.

normally if the opposition character is a villain the villain acts first, forcing the hero to respond.

in lord of the rings act 2 starts when Frodo commits himself the the concrete goal of taking the ring to Rivendel.

he must do this because the villain is already in motion, trying to take over the world and specifically trying to get the ring back.