The Unseen — Sabrina Devonshire

After gemstone smugglers murder three men, Kent Dunbar pretends to abandon his exploration of Vietnam's Mountain River Cave and his relationship with new love, Rebecca Devereaux. Imagining Rebecca has safely left the country, he plans to pursue the smugglers with help from Vietnam Veterans who served with his father in the war.

Rebecca is devastated by Kent's rejection. At the airport, she overhears men discussing Kent's mission. Rebecca convinces her best friend, Amanda, to stay and when the flight is cancelled, high-maintenance Bunny ends up with them as well.

While Rebecca and Amanda confront their men, first with words, then with naked flesh, Bunny suffers guilt over her whiny behavior and vows to toughen up and break free from her abusive past. But no one's safe in the jungle or underground labyrinths with murderous smugglers around. Will the adventurers prevail?