Neurosurgeon and newly appointed Chief of Surgery Billie Sutton has been there for Conrad and his daughter Gigi since the passing of their wife/mother and her best friend over 3 years ago.
Inspired by events that took place during Season 5 Episode 8 and especially that scene where it's apparent that Billie's feelings towards Conrad has significantly changed.
It's taken place from around that episode and beyond. So I suggest you catch up to that episode before reading my Fanfic.