Turns out, Malfoy has been a spy for quite a long time, feeding Lupin information via letters and secret meetings. He’d started informing a little after they’d been caught at the manor. Hermione connects the dots quickly, but no one else does, since Ron’s going on about how "that git didn't do shit when Hermione was being tortured by his crazy aunt.’ Hermione flinches at the mention of Bellatrix and holds her scar. It burns sometimes, randomly, and Hermione thinks it might be Bellatrix thinking about her. 