Survivants, cycle 2, tome 2
Erin Hunter2016

Darkness has struck at the heart of the Wild Pack. Whisper is dead—and Storm is certain that his wounds could only have been inflicted by another dog. Lucky and her Packmates are reluctant to believe her, but Storm is determined to face the truth: could there be a traitor in their midst?

Titre original : Survivors: The Gathering Darkness, book 2: Dead of Night (2016)