The Hollow Frequency

When Jessamine Park disappears the night of the junior Fall Formal, the police call it a runaway. Her best friend Mara Chen calls it wrong.

Mara has three things going for her: a methodical mind, a banned-from-IT best friend named Felix, and the old shortwave radio her late grandfather left her — along with a secret log of the anomalous frequency he'd been monitoring before he died.

Then the radio picks up a voice on 6.925 MHz. A voice that sounds exactly like Jess. Counting the days she's been missing.

Following the signal leads Mara, Felix, and Felix's engineering grad-student cousin deeper into a conspiracy that goes far beyond one missing girl. Someone has been secretly installing surveillance hardware in schools across four states, harvesting biometric data from tens of thousands of students — and selling it. Jess found the evidence. That's why she disappeared.

To get her back, Mara will have to triangulate a signal that keeps cutting out, infiltrate an abandoned quarry, and trust that everything her grandfather taught her about patient, careful attention is enough to find what no one else was looking for.

The Hollow Frequency is a propulsive YA thriller about surveillance, data privacy, the science of listening, and the kind of friendship that builds a transmitter from stolen parts and broadcasts into the dark trusting someone will hear it. Perfect for fans of Karen McManus, Maureen Johnson, and Jennifer Lynn Barnes.