Vesuvius, by Cass Biehn.
A young thief named Felix pulls off his greatest heist yet: the divine helm of Mercury. After stealing the sacred relic from a temple near Pompeii, however, pieces of his unknown past begin to surface in his memories.
Loren, a temple acolyte with ambition to rise through the ranks of the priesthood, has been plagued with fevered visions of Felix for years. The last thing he expects is for the boy of his literal dreams to stumble through the temple doors during an earthquake.
Felix's memories. Loren's visions. Mercury's helm. All are mysteriously connected to each other. Now, Felix and Loren must navigate the blood-stained labyrinth of politics in ancient Rome to make it out alive---assuming they survive the eruption of Vesuvius, first.