Who is Tanja and Stefan Castle from Inside Scientology: The Story of America's Most Secretive Religion and what is their importance?

Tanja and Stefan Castle were members of the Sea Org. They joined Sea Org as a couple, but after Stefan began having problems with David Miscavige, he was sent to rehabilitation off base. The group pushed Tanja to divorce him on a daily basis, but she refused. When Tanja finally threatened to leave the organization, she was held hostage and berated until she agreed to stay and divorce her husband. Meanwhile, Stefan, who'd finally gained his freedom, believed his wife had left him, He did not, however, give up hope and was able to smuggle a letter to his wife with help from the Headleys. As a result, they planned Tanja's escape, and on the designated evening Tanja jumped the fence of the base and the two ran away to freedom.