“Because the families choose the sacrifice. Each House makes one, once a generation. Traditionally, it’s the firstborn.” The uninflected blankness of a teacher reading from a textbook. “The firstborn what?” Laurent asked, setting down his coffee. “Child,” Sydney said. “The firstborn child.” “No.” Laurent stood up. “No. What is that? Sacrifice the firstborn child? Like some fucking Greek myth? No. This is the twenty-first century. That does not happen.”
What the heck else would "firstborn" mean. Even without coffee, this seems very obvious.
