The Firefly effect was intense and heavy on emotions. The bond between Walter Bishop and his son Peter seems unbreakable despite the disastrous impact his saving had on the parallel universe. However in the past episodes their relationship has been unidirectional because it seems Walter is desperate when Peter is quite confident when if he doesn't know what's happening. Even after what happened with Fauxlivia he has always managed to put one foot in from of the other. Don't look back, move forward. He has a goal in his life and won't give up for anything or anyone. Still his connection with Olivia is strong and it's sweet that the writers keep covering it while they work or investigate. It makes it even more authentic and freshen up the episodes with moving moments. However even if Peter is no Parker and definitely not a superhero it seems he has the ability to trigger a very technologically advanced device, the machine. Reciprocity was mostly about developing their interaction. Human-computer is a well known subject because we use smartphones or play video games everyday. But what's their influence on our evolution ? Do we live in symbiosis with the objects we have created ? We're probably as clueless as a clownfish dancing with sea anemones. It's the vicious circle of life and death. Will they win the war ? Could they defend themselves without studying and building the machine ? But asking questions is not enough, almost frustrating, so this installment was also about answering a few of them. The story was actually more twisted than Do Shapeshifters Dream of Electric Sheep?. It wasn't an other silver invasion but something entirely different in the end. It was almost like if they put two writers on the job and convinced them to compete instead of collaborating. One minor issue was made with an awkward revelation that could have been more subtle but overall it was an intriguing and puzzling tour de force ! And as often Walter was a barrel of monkeys. Wait ?!