Lur Gallastegi has published several adventure books before this publication, which in most cases coincide with the reality of foreign countries (Senegal, Sahara…). On this occasion, however, it offers us an adventure novel set in Donostia for boys and girls from the age of 10.

As the title of the book itself has suggested, the protagonists of this novel will pursue a secret: Peru, Aixa, Etor, Malen, Lander, Eira, Eana, Eider and Intza, who tells the story first person. All the neighbors of the Old Quarter and those who meet on the beach of Ondarreta coinciding with the beginning of the holiday.

However, Intza has not given a good start to the holiday. On the first day a stone will be injured in Ondarreta and it will have to spend several days without entering the water. Friends stay in shifts with Intza so he is not alone on the beach, and at those intervals, among other things, they investigate the origin of the beach stones. Where do the stones of Ondarreta come from? Is it true that there was a prison? Are there sirens at sea?

In this work proposed by Gallastegi, the reader gets into an adventure whirlwind that, like the sea turtles, will lead him to move further and further in. In it, the illustrations of the book, realistically elaborated by Iosu Mitxelena, help to follow the line of the novel; but above all, the structure of the book in short chapters and the numerous interviews between the protagonists, over and above the descriptions, help the reading. On the other hand, we recently said that the narrator is an adventurous protagonist, and that makes the reader identify with them, feel closer. I mean, living the anecdotes of this book as if it were a story that had happened to him or to his friends.

This is an adventure book that quickly reads underwater secrecy; an interesting novel that gathers many events that occurred during the holidays of a group of boys and girls. But in addition to that, this book is also a means to jump from fantasy to the world of reality, to delve into our history and, if you will, to get to know some aspects of the 1936 war.