I think this is a young adult fiction book, probably adventure and mystery.
I remember it being about a group of teenagers who discover secret tunnels under a city and start exploring them in search of a supposed treasure. At the beginning, the protagonist sees an albino girl coming out of a hole in the middle of the street and describes it as something strange, almost magical.
Later, this girl shows up as a new student at the protagonist’s school and becomes her friend. Over time, they form a group with other teens and continue exploring the tunnels together.
In one specific scene, they enter a room full of rats and use some kind of sound device to scare them away.
The albino girl is extremely intelligent, athletic, and highly skilled (kind of like a strategic genius). I think later in the story she betrays the group and keeps the treasure for herself.
I also remember this being part of a series. In the second book, the characters are older (around 16–17), and it’s revealed that the albino girl comes from a rich or possibly royal family from another country. The treasure was actually something important to her family (I think a jewel), and she hid that information to get the group’s help.
I read this around 2018, and I got it from my school library. It was likely intended for teenagers.
I’m from Brazil and I read the book in Portuguese, but I believe it was an international book that was translated.
I used ChatGPT to translate this because I don’t speak English very well.