 In the parallel universe , Walternate 's machine has been detected by the Fringe division and Fauxlivia and her team go to investigate . When Walternate tells them to stand down , Fauxilivia asks him about her recent mission to the prime universe and the part that she recovered . Walternate admits to her that the machine has been activated , having sacrificed his own son Peter to allow Fauxlivia 's son to live . Fauxlivia becomes distressed at Walternate 's actions , and later returns to Liberty Island to obtain the devices to allow her to cross to the prime universe , but is caught before she can use them . Walternate locks her away , seeing her as a traitor to his cause . 
