In the last book one member of the expedition from the O-220 was never accounted for. This is the story of Erich Von Horst.
Erich or as the locals call him Von got separated and captured by the Torodon (pterodactyls). There he meets Dangar a fellow prisoner from Sari. The two escape and form a friendship. While on the way to Sari they meet Skruf and are tricked into accompanying him back to his village with promises of friendship. Instead they are betrayed and forced into slavery.
While there Von meets La-ja a fellow prisoner. Von organizes a slave revolt and the three escape. They then have adventures in trying to return La-ja back to her tribe. They encounter the Gorbuse, an underground race of cannibalistic albinos. Then they have to survive the Mammoth men.
Von and La-ja make it back to her tribe. There Von kills the evil Gaz, wins the love of La-ja and the chieftainship of the tribe. At the end an expedition lead by David arrives looking for him. Von decides that he would prefer to remain in Pellucidar.
The next book in the Pellucicar series is a good solid adventure story. Nice to see that he didn’t forget about poor old Von Horst.