A Deadly Shade of Gold — John D. MacDonald

A long-ago face from a faraway past -- Sam Taggart dropped in from nowhere on the girl he'd left behind -- and on his old buddy Travis McGee. And at one o'clock that night McGee opened the door to Taggart's cheap motel unit to find his friend's throat neatly cut from ear to ear and his body lying in a lake of blood smelling like freshly sheared copper. McGee was left to inherit the legacy: Taggart's vengeance-driven woman and an ancient Aztec golden idol. The girl would plunge McGee on a wild and perilous trek which led from the Lauderdale beaches to the seething corruption of American expatriates in a distant Mexican town, to the lush highlife of the California jet set.