Because the Thracians were a simple and "simple-minded" people (by Greek accounts), Zalmos impressed them by building a secret underground chamber—a bothros —where he retreated for three years. He vanished from the world, and the Thracians mourned him as dead. When he reappeared in the fourth year, pale and changed, he convinced them that he had returned from the dead. This "resurrection" allowed him to teach them that the soul is immortal and that death is not an end. The Greeks concluded that this was a clever trick, labeling a political charlatan.