What on earth was he planning to do

In fact, from certain things, one could have noticed earlier that something was amiss. 

For instance, why did Angel insist that Sam personally check on his sister and Sophie when there was clearly nothing wrong with them and no accidents had occurred? What was the purpose of luring him into this room?

And why did Angel feel the need to follow him into the room herself? Clearly, it was for the purpose unfolding before his eyes. She intended to do something here, and in front of Ava and Sophie no less.

Sam quickly connected these dots, including why, instead of inviting him in when he knocked, Angel had blocked him at the door. It was all for this purpose. It meant that Angel was determined to carry out this particularly perverse act.

Was there really a need for this? Was it truly for the thrill, or was there something else at play?