You have been in trouble before. Going where you shouldn't. Curiosity.
This is Chapter 12: A Dreadful Discovery. Doon revisits the closed door in Tunnel 351 and finds a key lefts in its lock. As he opens the door he sees the Mayor sitting in an armchair, full-weighted, with clothes hanging on the walls. Doon shares his discovery with Lina, who in turn reveals her findings about Lizzie and Looper.
River Adventure
This is Chapter 14: The Way Out. Following the instructions they find iron ladder, leading down to a ledge on the riverbank. Within this space, Doon and Lina sees a door and a panel holding its key. As they do in they lit a candle, they discovered a much larger object labeled "BOAT."
Mysterious Path
Lets go!
This scene is in Chapter 16: The Singing. The city guards quickly catch Lina and march her to the Gathering Hall to face Mayor Cole, who says her behavior is dangerous and disloyal.
Journal: Train Ride
This scene is from Chapter 17: Away. They approach the boat and are safe on it. Doon pulls the rope free and they go down the river.
Here we go!
SPLASH
This is from Chapter 18: Where the River Goes. As Lina and Juliana goes off the boat, Doon, and Poppy stay on the shore, we found a path, and decided to follow the path, wondering where it would lead us.
Wait up!
This scene comes from Chapter 20: The Last Message. They name the children Star and Forest. Next, they discover a tunnel. When they explore it, they find a sheer ledge that drops into the darkness. But it's not completely dark—far below is a cluster of light. It's Ember. The kids realize that Ember has been underground this whole time.