The Silenced Echo. Zara Whispers's Pet Psychic Mysteries, #4

The rules of magic have changed, and for pet medium Zara, the new price of power is absolute silence. When her beloved community is rocked by the psychic coma of an ancient familiar-a casualty of her nemesis Malachi's rising ambition-Zara is left with an agonizing spiritual void. Malachi has discarded his quest for knowledge in favor of raw magical fuel, draining animal spirits to power his ascent to the "Silent Overlord." His trail of disappearing ghosts, dubbed the Ghostly Plague, leads Zara and her Fae ally, Lyra, to the stagnant depths of the Municipal Reservoir, a Sunken Forest hiding a sacred Fae Ley Line nexus.
To stop Malachi from corrupting this ancient power source and securing a permanent cross-dimensional escape route, Zara must master a dangerous new form of mediumship while navigating the chaos of a spirit-dense environment. With a skeptical scientist, Dr. Thorne, doubting her every move and a shady Imp, Snip, holding the only map, Zara must race to heal the living and rescue the dead before Malachi silences the entire magical world.