even as she drove , sophie 's mind remained locked on the key in her pocket , her memories of seeing it many years ago , the gold head shaped as an equal-armed cross , the triangular shaft , the indentations , the embossed flowery seal , and the letters p. s. although the key barely had entered sophie 's thoughts through the years , her work in the intelligence community had taught her plenty about security , and now the key 's peculiar tooling no longer looked so mystifying .