THE RETURN LINE
===============

The phrase RETURN ONLY is not a direction to come home. It is an
engineering instruction.

Maintenance signals travel inward from a surface node. The system is
built to prevent a clean signal from travelling outward. Channel 33 is
the maintenance return channel: a controlled route into the array, not a
conversation with whatever waits below it.

The resonators are not simply shields. They form a one-way barrier.

The line indicator flickers.

    RETURN ISOLATION: 71%

Then something transmits upstream.