The boundary god dies on the morning Tessa Venn is sent to measure a damaged ferry landing.
Tessa is a surveyor, not a soldier. Her chain, staff, and ink certify roads and settle disputes. But when she joins a measured route to save an injured ferryman, a mile folds into a few dozen yards, and soldiers begin marching through the line she drew.
The magic has rules. Ink binds the measurement. An oath gives it force. Distance must be exact. Every shortcut takes something from the land, and every command leaves a debt someone must pay.
Tessa’s rescue becomes an invasion. Rusk Halden’s army wants the valley, its causeway, and the dead god’s vacant authority. The defenders have fewer soldiers, divided loyalties, and no safe road behind them. Tessa must make maps that hold under fire, work with people who can refuse her, and decide which borders may move without erasing the people beside them.
At the eastern gate, victory will depend on a line that cannot be drawn twice. The campaign may end there. The larger war will not.
Draw the line. Pay what it takes.