Pretty Little Liars - Season 6, Episode 10: Soundtracks

(Flashback) Earlier in the night at the prom, the girls and Sara discuss if Charles would hurt Alison and what they should do when they begin to feel unsafe and leave the maze, then run into Mona. 

(Originally by Irving Berlin) Cece sings to the camera to the girls and Mona as they watch her encounter with Alison over the live stream from -A's surveillance room. 

CeCe sings to the camera that the girls are watching in A's surveillance room.