earlier, lethal doses of the alloy. Walter, who has lamented to Nina Sharp (Blair Brown) his need to have William Bell (Leonard Nimoy) back to make himself whole, realizes that the only reason the osmium-lutetium alloy became lighter than air was due to his own transgression into the parallel universe that has started to break down the laws of reality. To reverse those effects, Walter intends to use the idea of "soul magnets", microscopic devices that can be ingested by a person to call forth the soul of another. Walter believes Bell had arranged for someone in the prime universe to be his vessel, and rings the bell that Bell had bequeathed to Nina, believing it to be the instrument that will activate the soul magnets and call forth Bell. Simultaneously, Peter (Joshua Jackson) has decided to open up to Olivia (Anna Torv) and shows her the five data discs from the shapeshifters he killed after the doomsday device weaponized him. As he discusses it with her, Olivia hears the sound of the bell. She turns to face Peter, revealing herself to now be possessed by Bell. Production The episode was co-written by co-executive producer Josh Singer and executive story editor Graham Roland, while former Fringe producer Brad Anderson directed it. The return of the William Bell character to the series was inspired by Leonard Nimoy from earlier seasons. In his first appearance on Fringe in the first season finale, "There's More Than One of Everything", Nimoy requested that a bell be placed on his desk so that his character would be able to ring it as a play on the character's name. When the writers considered how to bring Bell back for the third season, they recalled this mannerism, and wrote it into the larger mythos, being the means by which Bell's mind emerged from Olivia's at the end of this episode. On March 3, Entertainment Weekly reported that actor Jorge Garcia would be making a cameo appearance in an upcoming Fringe episode. Garcia, who previously starred as Hugo "Hurley" Reyes from J.J. Abrams' Lost, appears as a Massive Dynamic guard that is smoking a bong with Walter at the start of the episode. Alan Ruck guests as Dr. Crick, the person behind the floating bodies. Ruck was approached by the show's producers having envisioned him for the role. Ruck described the character, "He is no dummy... and he