'And if you'd made the right decision in the first place then there would have been nothing to tell!' Cass exclaimed, feeling as if he was going in circles. 'Fuck Monty, you act as if I wanted to tell, or know, or whatever...' He sighed, almost collapsing back onto the bed. 'Your choice was to join the Death Eaters, my choice was to fight them - we're both paying for our choices now, though as far as I can see, you've got the sweeter deal here.'
He looked at Montague, dead serious. 'You still have your family, I've lost my mother. You also very much alive, which is something I very well might not be once Rodolphus realises that I'm not cooperating with him. Not to mention that Miles might be the one who gets ordered to kill me. What have you lost so far? Your reputation? The freedom to do whatever hell you want without the risk of getting caught?'
He snorted as Montague continued. 'Yes, because I'm so likely to run off and tell Rodolphus, aren't I?' He rolled his eyes. 'In case you didn't notice, he's not exactly my favourite person in the world.'
'But to answer your question, you should tell me because if you were doing something like that you'd be out of trouble faster than you were in it. I'd may have resigned, but Percy listens to me. If you could convince me, I'd convince him, and then your troubles would be over.' Not that they could be called troubles. Hell, Monty didn't seem to know what the word meant.
He purposely didn't mention Percy's last name. Or their relationship. Once he did, Montague would probably stop speaking to him and then he'd never find out what it was Montague claimed to be doing.