LXXVI. Key
Sirius left Marlene's with a plan.
He was going to prove to her that he did love her, did care about her.
(Even if he wasn't so sure either of those things were true beneath the veil of the love potion.)
He didn't know what the key to her heart was - had no idea, in fact - but he'd wooed other girls with flowers and smooth lines, so he went back to his flat and began to map out a plan.
He'd need nine dozen roses, to start.
And he'd need his battered old trunk from first year.