“Five-Twenty-Ten” is episode seven of season five of Fringe.
At the end of the previous episode, “Through the Looking Glass and What Walter Found There”, Peter started seeing the world in the same way. He’s now watching two Observers interact in the same way; one gets in a car with the other. Peter steps out into the road, stopping traffic. Then events unfold as he’d just seen them, except the Observer now misses the car, thanks to Peter stepping into the road and delaying it. Peter calls Anil and tells him there’s something he needs help with.
Peter arrives back at the lab with more fuel for the laser. He left without Olivia because she was asleep and he isn’t sleeping. Loyalists arrive outside, but head off again. Tape 5 is then retrieved. On the tape, Walter explains about how they need to get two beacons of the type first seen in “The Arrival”. Two of them are at Kelvin Genetics, in a private storage facility belonging to William Bell. Astrid realises that’s why Walter took Bell’s hand. Walter says that was why Bell was in amber. Astrid says that’s not the only reason; Bell betrayed them to the invaders to gain favour. Walter recounts what happened. Astrid tells him that’s the plot of Marathon Man. Peter and Olivia explain what happened and how the Observers found them, thanks to Bell’s betrayal, before they could do the plan and they had to go into amber.
The lab is damaged and the doors are hidden behind debris; Peter says where they are using his Observer tech, though he lies about this. Anil calls Peter; he was unable to swap the briefcase with the Observer’s, because the Observer didn’t forget it. Peter says he will meet Anil. They decide they need technology from Nina Sharpe to get through and the others head off to meet her and explain what they need to do. She can get them something that sublimates the rubble.
As this is being retrieved, Nina speaks to Walter; she asks him if he’s seen any change in his personality since the missing bits of his brain were implanted. He has. Nina doesn’t see the man he was before, but says Walter will know better. Walter says it’s different this time. He is different. Peter will not let him become that man again.
Anil is explained to Peter what happened. It seems the Observer, Royce, was talking on his communicator, which Peter hadn’t seen, and therefore wasn’t distracted and didn’t forget his briefcase. Peter says Royce will be at a restaurant next; he will switch the briefcase there. He wants Anil to go and wait outside an Observer precinct, where Royce and another, Mueller, will enter. Call Peter when they do.
Walter is being changed by the reimplantation of the removed parts of his brain, and depending on Peter to stop him from becoming the man he was might not be a good plan. Because Peter is being changed himself by the Observer tech he implanted.