That was the reaction he was looking for. Severus latched onto it and exploited it for all it was worth; suddenly, it didn't matter that this was about Sirius bloody Black or the cursed werewolf or anything else that he normally loathed. Now it was about his interests and what he might gain. If he inadvertently helped Lupin to understand the situation a little better, he wouldn't care either way.
"I do," he said slowly before straightening up and letting a smirk play on his lips. Holding the power felt good and he wasn't about to let it fizzle out before he'd gotten a firm grip on it. "If you're so worried about your precious mate, you might be hard pressed to find a better way to go about fixing the situation without my help." It was said so confidently that he was even surprised at how good it made him feel to hold this over Black.