Excerpt from The Invisible Guardian by Dolores Redondo, plus links to reviews, author biography & more

The pathologist gave Jonan an appraising look, weighing his youth and likely knowledge, then took the notes offered to him by the technician and flicked through them quickly while leaning over the body. It was a look Amaia knew well. A few years earlier it was she who'd been the young deputy inspector in need of instruction in the mysteries of death, a pleasure that, as a distinguished professor, San Martín never let pass him by.

"Don't be shy, Etxaide. Come closer and perhaps you'll learn something."

Dr. San Martín put on a pair of gloves he'd pulled out of a leather Gladstone bag and gently palpated the girl's jaw, neck, and arms.

"What do you know about rigor mortis, Etxaide?"

Jonan sighed, then started to speak in a voice similar to the one he must have used when answering the teacher in his school days. "Rigor mortis is caused by a chemical change in the muscles. It is evident in the eyelids first and spreads through the chest, trunk, and extremities, achieving maximum stiffness after around twelve hours. The body starts relaxing again in reverse order about thirty-six hours later, when the muscles start to decompose due to the effects of lactic acid."

"Not bad. What else?" the doctor encouraged him.

"It's one of the principal indicators used to estimate the time of death."

"And do you think you can make an estimation based solely on the degree of rigor mortis?"

"Well . . ." Jonan hesitated.

"No," declared San Martín, "absolutely not. The degree of rigidity can vary according to the deceased's muscle tone, the temperature of the room or, as in this case, the environment, since extreme temperatures may give the semblance of rigor mortis, for example if a cadaver's been exposed to high temperatures, or when a body suffers a cadaveric spasm. Do you know what that is?"

"I think that's the term for when the extremities tense at the moment of death in such a way that it would be difficult to relieve them of any item they might have been holding at that precise instant."

"Correct, which is why forensic pathologists have to shoulder a great deal of responsibility. They shouldn't establish the time of death without keeping all these factors in mind and, of course, you can't forget hypostasis . . . you might know it as livor mortis. You must have seen those American TV series where the forensic pathologist kneels by the body and establishes the time of death in less than two minutes," he said, raising an eyebrow theatrically. "Well, take it from me, that's all lies. Analysis of the quantity of potassium present in the vitreous fluid represents a major step forward, but I'll be able to establish the time of death with any certainty only once the autopsy has been carried out. Now, based purely on what's in front of me, I can state: thirteen years of age, female. Taking into consideration the temperature of the liver, I would say she's been dead around two hours. Rigor mortis hasn't set in yet," he confirmed, palpating the girl's jaw again.

"That fits in more or less with the timing of her call home and her parents reporting her missing at the police station. Yes, two hours, if that."

Amaia waited for him to stand up and then took his place kneeling next to the girl. She didn't miss Jonan's look of relief at being released from the forensic pathologist's scrutiny. The girl's eyes stared blankly into infinity, and her mouth was half open in what looked like surprise, or perhaps a final attempt to inhale, giving her face an air of childlike amazement like a little girl on her birthday. All her clothing seemed to have been slit cleanly down the middle from her neck to her thighs and was pulled open to either side, like a half-unwrapped gift. The gentle breeze coming off the river moved the girl's bangs a little, and Amaia caught the scent of shampoo mixed with the more bitter aroma of tobacco. She wondered whether the girl had been a smoker.

Excerpted from The Invisible Guardian by Dolores Redondo. Copyright © 2016 by Dolores Redondo. Excerpted by permission of Atria Books. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.