Eighteen-year-old Filipino American Ruby Santos has been unmoored since her mother's death. She can't apply to art school like she's always dreamed, and she and her father have had to move into the basement of their home and rent out the top floor while they work to pay back her mother's hospital bills.

Then Ruby finds out her father has been living a secret life as a delivery person for a magical underworld--he "jumps" train lines to help deliver packages for a powerful family. Recently, he's fallen behind on deliveries (and deeper into alcoholism), and if his debts aren't satisfied, they're going to take her mother's house. In an effort to protect her father and save all that remains of her mother, Ruby volunteers to take over her dad's station and start jumping train lines.

But this is no ordinary job. Ruby soon realizes that the trains are much more than doors to romance and adventure: they're also doors to trafficking illicit goods and fierce rivalries. As she becomes more entangled with the magical underworld and the mysterious boy who's helped her to learn magic, she realizes too late that she may be in over her head. Can she free her father and save her mother's house? Or has she only managed to get herself pulled into the dangerous web her father was trapped in?