Look at all the scenes in this episode that have nathan in it. He is wearing a necklace around his neck, you can not see at any time what is hanging from the band, but the band looks very much like the band of the necklace Peter is wearing.
Could they both be wearing helix necklaces?
If so...what does this mean?
EDIT:
MY THEORY AFTER REWATCHING THE EVENTS SEVERAL TIMES..
Nathan bumps into Ando as he is bringing the paper to Hiro's father. As any good pick pocket knows a bump is enough to distract a person to either pick a person's pocket..or in nathan's case slip a picture into the paper Ando is holding.
Next we see Nathan entering Peter's aprtment with his mother inside. While he was still outside the aprtment I believe Nathan planeted the next photo on the wall outside the door. He then calls his mother evil and throws her out and she finds the photo he planted.
Nathan is wearing this HELIX necklace for a reason.
He was burned in the explosion that "killed" his brother. He blames his mother and the people she worked with. The villain of this season finds Nathan and tells him he will heal him on the condition that he help with his ultimate revenge. Nathan wants revenge as well and joins forces with the villain and helps plant the photos. Nathan is feeling guilty over everything that has occured and looks in the mirror while at the bar and sees what he looked like before the villain and his society of helix wearing necklace guys healed him. Anyway that is my theory
