"Dinner with Cygnus," he nodded, as he took a sip of his drink. "Well, you could at least not tell you father about the letters? I'd want to take a look at it myself and I know him knowing about it he'd be all over the thing the minute you inform him."
He didn't really hate the authoritative figure of his father-in-law, but he'd be best not tinkle with this now. Rodolphus wants to hunt down the sender himself, torture it to slow death - before he extract any information about why they were sending those letter.