 A shipment of heads stored in cryogenic storage is hijacked , though one of the hijackers is killed by a guard , and bleeds a mix of blood and mercury , identifying him as a shapeshifter from the parallel universe . The Fringe division discovers an undamaged device they believe is used by the shapeshifters to take another 's identity . Olivia Dunham ( Anna Torv ) gives the device to Nina Sharp ( Blair Brown ) at Massive Dynamic ; with the intact device , they can use it to examine the device of the first shapeshifter that tried to kill Olivia in the episode " A New Day in the Old Town " . They are unaware that this shapeshifter has taken the form of Olivia 's partner , Charlie ( Kirk Acevedo ) , ordered to find out what she learned from William Bell ( Leonard Nimoy ) when she was temporarily taken to the parallel universe . 
