Cass took a deep breath, knowing he couldn't avoid this any longer. Surely Montague would pity him at first, but... not so much when it was all out.
'Rodolphus found out,' he said plainly, getting it out there. 'He intercepted a letter, I think, and no matter if that is how he found out or not, he used the knowledge to find and kidnap her.'
He paused for a moment, looking at Montague. 'Miles got the questionable pleasure of telling me that if I wanted her to stay alive I should spy on the Aurors. Stupidly enough I agreed, thinking I could handle it on my own, find out where she was held, fight back once I knew... I, of course, was wrong, which is why I'm presently under investigation and not an Auror any more.'
'Or part of the reason at least,' he amended, though he did not expand on his second reason.