John Carter first meets Zan Dar when he and U-Dan are imprisoned on Sasoom. After the Morgor Vorion is also imprisoned with them, the four men conspire to escape. Vorion however only wants to help them if Zan Dar promises to take him to Zanor and give him asylum there. Zan Dar agrees to this condition, although he cannot promise Vorion that his people will let him stay. The four manage to get out of their cell by picking the lock, and by pretending to be Vorion's slaves they can venture outside into the streets. Together they steal a ship and free Dejah Thoris and Vaja. John Carter is captured again, however, but Zan Dar manages to get away along with Dejah Thoris, Vaja, U-Dan and Vorion.
Zan Dar is not seen again in the rest of the book. At the end of the story John Carter arrives in Zanor and expects to be reunited with Dejah Thoris, but it is not revealed if she and the others are actually there.