Ghost Frequencies. THE ECHO TRACERS, #2

Now officially partnered, Maren and Agent Elias Vance are a formidable team in the FBI's new Resonance Division. While Maren is teaching a new class of agents how to "hear" the past, her skills are put to the ultimate test when a young tenant in a historic D. C. apartment building reports strange "ghosts"-voices only he can hear. The building is slated for demolition, but Elias senses a connection to a decades-old, high-profile political assassination originally ruled a suicide.
Maren scans the building's ancient plaster walls and retrieves faint, trapped sound waves-the "ghost frequencies" of a murder that has haunted D. C. for twenty years. As they uncover a conspiracy reaching the highest levels of government, the real danger begins. The person who covered up the original crime in the 1990s is still powerful and still active. This shadowy villain launches a "noise campaign" designed to drive Maren mad, using sophisticated, directed-energy sound waves to disrupt her balance, focus, and sanity.
Elias must anchor Maren to reality while they work against time to expose a killer protected by D. C.'s elite. They must solve the cold case that echoes in the walls before the psychological strain shatters Maren-and their relationship-forever.