"—Kingsley and Mr. Weasley explained it all as well," Harry pressed on remorselessly, "Once I'm seventeen, the protective charm that keeps me safe will break, and that exposes you as well as me. The Order is sure Voldemort will target you, whether to torture you to try and find out where I am, or because he thinks by holding you hostage I'd come and try to rescue you."
Uncle Vernon's and Harry's eyes met. Harry was sure that in that instant they were both wondering the same thing.