The signal was first detected on March 15, 2204, by a routine monitoring sweep of the Lake Huron frequency spectrum. It broadcasts on 4,625 kHz — a frequency in the maritime medium-frequency band that has been allocated, since the pre-collapse era, to emergency communications. The signal is analog. It is a human voice. The voice reads names.

The voice is female, mid-register, with no identifiable accent. It reads each name clearly, with a pause of approximately four seconds between names. The reading is continuous — it does not stop for periods of silence, does not loop, does not repeat. New names are added at a rate that Signal Intelligence has determined corresponds, with unsettling precision, to the mortality rate of GLMZ's registered population. Specifically: the names read by the voice are the names of people in GLMZ who died within the previous 72 hours. The correspondence has been verified across 4,017 consecutive days of monitoring. The error rate is zero. Every name matches. No names are missing. No names are wrong. The signal knows who died, and it knows within three days.

The signal originates from coordinates 44.1°N, 82.7°W — a point in the central basin of Lake Huron, approximately 120 kilometers from the nearest shore. Triangulation from multiple receiving stations has confirmed these coordinates repeatedly. The signal strength is consistent with a stationary transmitter of moderate power. There is, however, nothing at those coordinates. Surface survey by boat has found open water. Sonar mapping has found lake bottom at a depth of approximately 60 meters, with no structures, no objects, and no anomalies of any kind. The water column is empty. The sediment is undisturbed. The signal broadcasts from a point in space that contains nothing capable of broadcasting.

The Signal Intelligence Division has maintained continuous monitoring of the Lake Huron Signal for eleven years. In that time, the signal has not deviated from its pattern. It has not ceased, even briefly. It has not changed frequency, modulation, or broadcast power. The voice has not changed in timbre, pace, or inflection. It reads names of the dead with the steady, uninflected cadence of someone performing a task that is routine but not careless — a task done with attention but without emotion. Analysts who have listened to extended recordings describe the experience as "not disturbing, exactly, but permanent" — a sound that, once heard, occupies a space in memory that it does not vacate.

Seventeen hypotheses have been formally proposed to explain the Lake Huron Signal. They range from the technical (a previously unknown natural phenomenon that coincidentally produces human-sounding audio matching real names) to the conspiratorial (a GLMZ intelligence operation designed for purposes unknown) to the frankly metaphysical. None have survived rigorous analysis. The signal remains unexplained, uninterrupted, and accurate. It is, as far as the Division can determine, exactly what it appears to be: a voice in the lake, reading the names of the dead, and it has not been wrong yet.