Act 2 will show the protagonist becoming a hero and take his destiny into his hands. This is the reaction to book 1.
Now that we know how screwed the hero’s life is, the hero is ready to wake up from the ashes and take his destiny into his hands.
Act 2 forces the hero out of his comfort zone (his normal life) and into the unknown (something emotionally scary happens to him).
The true enemy reveals itself.
The hero is faced with something new, something even bigger than he imagines, that will make him feel hopeless for a while. The stakes are heightened and a secret is revealed, something the hero did not even envision.
The hero must live with the consequences of book 1. Sometimes the author sacrificed a character that he needs later on, so this is the time to resuscitate him.
EXAMPLE: In the Lord of the Rings, Tolkien brought back Gandalf in book 2 after suggesting he was killed in book1.
The hero sacrifices something. The hero fails to save the day and everything he held dear is taken away from him. His situation is worse, his true identity revealed or his true options are revealed.
The main character needs to fix more things about himself, face his demons, resolve his grudges and instabilities.
Book 2 is the point of no return. The character realizes how far the enemies will go to get what they want. The hero will feel hopeless and go through a desperate moment. The hero has lost someone like Peetra in The Hunger Games by Suzanne Collins or the hero realizes that his last line of defense is gone. Gabry feels that there is nowhere to go and she is not different from a zombie herself in The Forest of Hands and Teeth by Carrie Ryan.
At the end of book 2, hope is in the horizon, but we cannot really see it already. The hero is given a key to defeat the villain even if he is exhausted and beaten down or even injured.
EXAMPLE: In Twilight, Bella learns that her true enemy is the Volturi. That’s the surprise.
Because of what she learned from book1, Bella thinks she knows what to expect from the vampire world. She is ready to take her first steps onto her path or destiny and the core conflict (Bella will meet the Volturi, the overlords of the vampire race).
Bella has chosen her camp. She is with the vampires and she wants Edward back. She has embraced her new life and she’s ready for what’s coming, but he is nowhere to be found. When she knows where to find him, she leaves the comfort of her home and runs to him in Italy. She decides to act and brave the danger to save him and be reunited with him.
Bella learns that the love between a human and a vampire is not allowed. She needs to become a vampire if she wants to live. Her life is in danger. Bella cannot anymore choose to stay human; she will have to sacrifice her past and forget about the people she loves.
Example, in act 2 of The Immortals, Damen is fading and pulls away from Ever due to poisoning. Ever needs to find a way to save him, but fails. In book 2 and 3, Ever is still trying to find an antidote to save Damen, but fails again. However, she discovers her true enemies and takes confidence in herself.
Johnson, Elana. "Writing a trilogy, Part Two: Book Two."