Regulus is already mentally scrambling for an answer, something to explain it all away. He's always been a good liar, but it's also always fallen short when it comes to Sirius. Still, he's almost ready, prepared to drawl something out lazily, but Sirius is piecing things together too quickly.

It would be worse if Sirius thought they'd fought somehow, right?

Still, his heart is sinking. Just a little. (The cruelest part of him still sometimes wonders which of them Remus would pick, if forced.)

"Huh what?" is what he finally settles on, lamely. Perhaps a fight would have been better.