Tonight, ABC’s Nightline will air its first part in a series on Scientology.

And now some senior insiders who have left the church are leveling disturbing accusations against the current leader, David Miscavige. Marty Rathbun, Amy Scobee, Bruce Hines and Mike Rinder each dedicated more than 20 years to the Church of Scientology, as members of the Sea Organization, or Sea Org, the equivalent of the church’s clergy. They tell co-anchor Martin Bashir they left in part because the 49-year-old leader, Miscavige, struck subordinates numerous times and encouraged others to do the same.