This is also similar to Jordi standing up for Evelyn earlier in the cafeteria by calling out the bullies.
Also, when Mike finally discovers that his new friends aren't really his friends, only using him to get closer to and hurt Mara, he snaps. He calls them out on it and leaves. Later lampshaded by his friends how awesome it was for him to do that.
Another one goes for Mike when he goes over to Mara and discovers her horrible home life. He's able to handle the situation well enough and even gives Mara her First Kiss and makes a Love Confession. Doubles as heartwarming.
Mike: Mara, you don't have to tell me anything you don't want to. Just know that everyone and me are here for you. Okay, little baby girl?
Mara: T-thank you.
When he receives the news that his name was found on a note near Dexter's body, Matt leaves the cafeteria so Mara decides to follow after and try to help. It's an awesome moment showcasing her attempts to break out of her shell and look out for her friends, something she often struggled with before this.
Following this is another moment for a character overcoming their insecurities for the sake for their loved ones, that character being Matthew. The moment he realizes his friends could be targeted, he sucks it up and faces them to tell them this information. Keep in mind that this is happening after his disastrous date where he rejected Evelyn, and thinks everyone pretty much hates him for it. He might be a jerk sometimes, but there's no denying his Hidden Heart of Gold is there.
Rose's Character Development is one of the highlights of the book, so it's only natural that it would be listed here.
The climax. To sum it up, our protagonists have been locked in the school. They are able to keep a calm head and look for an exit. Matt in particular takes on the role of The Leader and instructs everyone to look for Jordi while he looks for an exit. He also tells them to look after each other and runs off. When everyone regroups after finding Jordi, she reveals her to be the murderer, and it's nothing short of a chillingly awesome reveal. Mike gets to do a Heroic Sacrifice (even if it was reckless) that buys Matt time to disarm Jordi and tells Mara and Evelyn to get Mike and themselves to safety. A fight ensues between Matt and Jordi, who proves to be a stronger foe, but Matt doesn't give up and opts to taunt her to win the psychological fight.
