Seamus rubbed his face in his hands and let out a low groan, not wanting to draw attention to them. "You have no idea how bad I want to tell you. But I can't. Not only for my safety, but for the handful of people involved. All I can tell you is that it's really important and that while it could be a great help to everything that's going on out there," he said, waving his hand around, motioning that he was talking about the war, "it could also get us in trouble if anyone found out what we're doing. To the point that we could get sent to Azkaban."
Taking a deep breath, he looked straight into Dean's eyes - as much as he could anyway, since his mate was miles taller than him now - to show him he was being completely serious. "It's big. Huge. And it involves my Patronus lessons. But that's as much as I can tell you. I'm doing it for you though. You and all the other muggleborns who are getting sucked up into this bloody fucking war. You mainly though. I don't know what I'd do if I lost you to this shite. So just please...please trust me when I tell you that I honestly can not tell you what's going on, but the moment that I feel it's safe enough, I'll tell you everything."
He took another deep breath. Seamus hoped that it all made sense, and he didn't actually tell Dean anything other than the Patronus bit. Everyone's identities were still safe.