Sister Sandrine's distraught, to say the least. She just discovered that of her four emergency contacts she's supposed to try and reach if the floor panel in the church is ever broken, three are very recently dead. And the fourth, her absolute last measure, isn't picking up either.
This means that the upper echelons of the brotherhood have been compromised. Not good.
Silas appears, and tells her that all four men are dead.
Sister Sandrine realizes that those four men were the only ones to know the secret the brotherhood had been protecting for generations. All is lost.
Silas kills Sister Sandrine for insulting Opus Dei.