The Neptune is gone, stolen by the Indian guide Moc, or maybe by Guiana-Capac's malevolent gods. The last members of the ill-fated expedition: Silver, Dantzig, Livesey and Bonnet, are stranded in the ancient city. Far from being broken however, they will face head-on what lies inside the gargantuan ruin, each for his own reasons: revenge, duty, gold... or to rescue the beautiful Lady Hastings. For Moc isn't done with them, and he has plans for Vivian.