HELIOGRAPH — Signals Across the Iron Valleys

The line went dead at Cold Hollow and you are the new signal-keeper. Turn brass mirrors to walk a beam of sunlight across a hand-drawn valley and into the receiving station — then learn to split white light through a prism into three colours for three valleys, to husband a beam through fog that drains it, and to arrive on the beat while army shutters open and close. Twenty-four stations across five chapters, every one machine-proved solvable, with an honest par and a quiet score of plucked strings and glass bells.