Across the table was Rainer Melucci, whose expertise in electronic eavesdropping protection and antibugging services took him into the home of Tom Cruise in Los Angeles and the offices of the Church of Scientology. He said he was practically investigated by the church, which conducted several rounds of interviews with him while deciding whether to employ him. The most memorable part of that process was a private screening of “The Firm” in Mr. Cruise’s home theater.