Many are shocked to see Peterson, who remained relatively under-the-radar the entire season, in the final four – including host Chris Harrison.
"Who knows how he got there but he's there," joked Harrison during a conference call with reporters on Thursday. "It doesn't surprise me that [the others] are there because Rachel floated with the stronger alliance and Chris and Sarah played well. Whether you like Chris or not, whether you like Sarah or not, they won a lot of competitions, they played really hard and they gamed really well.”
While the outcome will be revealed on Monday (8 p.m. ET), it's safe to say that Trueheart had a tough time when the finale was taped. (See her backstage meltdown below.)
"Are you f––ing kidding me? What is wrong with you?" Trueheart shouts through tears.
Harrison says a number of factors led to the explosion of emotion, including seeing Michael Stagliano after he revealed that he does not want to pursue a relationship with her.
"Facing Michael was very difficult for her," Harrison told PEOPLE. "It is very emotional and it is tough on Rachel."
However, that may not be the whole story.
"The game itself is also something that Rachel is involved in, so she deals with Michael and then she also has to deal with the show," said Harrison. "It's a very volatile situation."
In fact, Harrison calls Monday's show the most disturbing Bachelor Pad finale ever.