Continuity mistake: Just after Olivia has killed Mr. Montana and everyone goes running up to see what has happened, Phoebe waves to Paige through the window of the Calloway's house which is shown to be right next door to the Montana's house. Earlier in the episode it had been established that they lived across the street.
Continuity mistake: When Chris orbs to the manor after Paige has returned home, his hair is brushed to lay mostly flat and behind his head, with a part on the left side of his scalp. When he comes into the kitchen shortly thereafter, his hair is shaggy and unkempt, with a part in the middle.
Continuity mistake: When the main Calloway throws the clear bottle with the green potion at one of the enemies, the shot cuts and it's now become a white bottle.
Answer: "Hush, Hush, Hush" Paula Cole.