Remus lets the silent protract, unhelpfully, with his lips tucked in between his teeth to keep from smiling in a way that might have been—not unkind, but easily misunderstood. His eyes still crinkle at the corners despite his efforts, though, despite the fairly ruthless math he's doing behind them. Seventh year. A couple more months and William will vanish into the world of adulthood and professions and grown-up relationships. It's a world Remus knows he'll be largely excluded from, and—if Voldemort doesn't win, if they don't all die—maybe he'll see him in passing, in Diagon Alley or something, but he'll never really have to explain himself.

Also: hormones.

So before the silence goes from awkward to unbearable, he shows mercy.

"Are you," he says, but even if David Bowie and Elton John walked in and personally loosened his collar and told him to relax, he wouldn't be brave and progressive enough to outright ask if a near-stranger was queer. Option B: "Maybe when I'm not sick and you're not studying, we could go for a walk." He grins, hopefully. "For my immune system."