The Signal Beneath Lagos

The first reports came from the subway engineers.

A low-frequency vibration, steady and patient, pulsing beneath the concrete arteries of Lagos.
Not mechanical. Not seismic. Something older — and impossibly precise.

When the university sensors confirmed the pattern, the data resembled a heartbeat.

Not human.
Not animal.
Something else.

The Signal marked the second known disturbance in the Third Arrival timeline, and unlike the first, this one was growing stronger.