The story

Every night the red moon rises, Ivar loses the shape of a man, and in all this fjord there is one hand only that can carve the rune to lull him. Last month, that rune already broke once. You read the grain of stone before you ever raise the hammer, and his grain is the one thing your palm never finds.

In a frozen fjord, a hand that knows how to cut runes is treated as rune priest and smith at once. Sigrid was given hands that feel the grain of stone and iron in the palm before the chisel is even set to it, and so the tribe hands her the most dangerous carving of all. Ivar, the youngest jarl the tribe has, loses the shape of a man each time the red moon rises, and the only thing holding him is one lulling rune wound around his arm. That rune splits along the grain a little more with every month, and the next red moon comes without fail. The tally board writes down the tribe's talk and every place a person may go, all of it without a gap, and leaves only the one square beside Ivar's name empty to the end.

The night before the red moon, when Ivar tightens the chain with his own hands and says, if I can't say your name in the morning, that's when you run.
The moment your palm reads the grain before the chisel touches it, and you put a finger on the place a runestone will split, the one everybody swore was sound.
The night the lulling rune failed, and you learn from the tracks left in the snow that the wolf sat down at the forge door instead of the village and held there until morning.