Bishop realized something he wasn't suppose to forget. He wasn't suppose to ever let Peter return to his universe. Or there would be a catastrophic price to pay. So the watcher left a flyer for agent Denim at the bar, with this clue Walter was able to remember.
"The Monkey House". For the past six week Boyles and Massive Dynamic secretly gathered the cortexphan children and teaching them to heighten their abilities.
Walter's plan is to use the cortexphan children's psychic ability to travel to the other side. These 3 people and agent Denim used their ability to travel to the other universe to save Peter. They are suppose to be the guardians that were put together by Walter and Bell and trained to save the world. But this episode shows that they were only trained for transportation purpose and it seems like its only one way. Because one of them dies after a few minutes upon arriving. The girl got sick. and then She blew her self up and her boyfriend together into ashes? There were nothing left of them. So much for guardian. I guess agent Denim is left to save the world again.