In the world before, Sara Weyer is a mathematician on the verge of a breakthrough-a way to harness the gaping blackness between numbers. But something is hiding in that darkness. Something not meant to be found. Enter the man in black. He is a gaunt figure, pale skin, his tailcoat draped behind him like a pair of folded wings. He comes into the Weyer home claiming good intentions-but now no one can make him leave. As his grip tightens...