When we first meet Marcelo, we learn that his life is pretty good. He gets paid to have brain scans, and has a summer job training equine-therapy horses. Plus his parents are wealthy, and he lives in a swanky tree house. Seeing a family with so much invested (both emotionally and financially) in being upper-class gives us a big ol' sense of foreboding. We need to see that Marcelo's got a privileged life; otherwise, he's got nothing to lose.
Turns out Marcelo's dad Arturo, an attorney, wants Marcelo to work at his law firm for the summer. He'd also like it if Marcelo would consider going to Oak Ridge High in the fall instead of returning to Paterson; both the law firm and Oak Ridge represent the "real world" Arturo thinks Marcelo needs to experience. If that's not conflict, we don't know what is: Marcelo's being challenged to deal with people who don't get him, when he's spent his whole life quite happily surrounded by people who do.
While working at the law firm, Marcelo discovers a picture of a girl named Ixtel who was severely injured when the firm's biggest client, a windshield manufacturer called Vidromek, produced a defective product. We can't think of a much bigger crisis than losing half your face, but that's Ixtel's crisis. Marcelo's is deciding whether or not to do the right thing and tell Ixtel's lawyer that Vidromek knew about the defect in the windshields. If he tells, his family could lose everything, including the funds to send him to Paterson. If he doesn't tell, Ixtel will continue to live in pain, and that's not right.
After making the decision to help Ixtel rather than his father, Ixtel's lawyer, Jerry Garcia, takes Marcelo to meet her at the convent where she lives. She's wicked grateful (hey, this book takes place in Boston, we had to use their favorite adverb at least once) and gives him a kiss. Marcelo has finally done the right thing, and Sandoval and Holmes have paid the piper. Except for some thorny interpersonal issues with Jasmine, things in Marcelo's life are as they should be. He finally gets to process what he's learned, after a hard journey to learn it.
Marcelo's resigned to going to Oak Ridge, and even though he may not be thrilled about it, he knows he can deal. And even though Jasmine had shenanigans with his pops, Marcelo decides he can forgive her. And by "forgive her," we mean "move to Vermont with her and live happily ever after." Okay, so maybe happily-ever-after doesn't exactly exist in the real world, but Marcelo's discovered he can handle a few ups and downs. Especially if Jasmine continues to kiss him on the cheek and set off the string section in his brain.