Standing up a bit at the werewolf's words, he watched him carefully before returning to the potion, stirring carefully according to memory. It turned into a lovely lavender before shifting into a fragrant sky blue.
"I would give you my word if you let me do what I need to. Knowing you and your ilk, you'll likely try to intervene, and that I will not deal with." Severus shot an accusatory look at Lupin quickly before returning to the potion.
"It shouldn't be harmful, in any case. Apparently whatever was already done to him is far worse than anything I might do."