Sirius texts the wrong number (I wonder who it is) and surprise surprise. It's Remus. This is just a story where Sirius is an annoying little piece of schist and they slowly fall in love. And guess what? I'm not telling you the plot twist. (Curses a bit)
Disclaimer: I DON'T OWN ANY CHARACTERS UNLESS I SAY OTHERWISE. THEY ALL BELONG TO J.K.ROWLING (unfortunately).