Dr. Magnus is in Italy to lead a covert meeting on abnormals and new medical findings, leaving Will in charge of the Sanctuary with Ashley, Henry and Bigfoot.
Magnus's trip to Rome proves more eventful than she anticipated when she encounters Nikola Tesla, an old friend from college with whom she clearly has a long history. Tesla informs her that she is in grave danger with the Cabal quickly moving in. Before any further explanation can be made, Tesla whisks Magnus away under Rome's city streets into a series of ancient catacombs in an effort to shake the Trackers.
As they ward off their pursuers, Tesla discloses his whereabouts for the past six decades, after his supposed death. It is apparent from their discussion that Tesla was one of an elite five who, with Magnus, belonged to an exclusive league of science and medicine. But Magnus is shocked when he reveals what he has been doing with his exceptional aptitude since their last meeting.
Back at the Sanctuary, Will has his own troubles. Something has been ravaging areas of the Sanctuary and attacking residents. With Henry suffering from the flu and Ashley nowhere to be found, Will starts his own investigation, leaving no one above suspicion.
There is good reason for Ashley's disappearance. Duped by a message to meet Squid, Ashley plays into the hands of the mysterious John Druitt. Druitt uses his cunning to keep Ashley's attention while explaining that Magnus is in immediate danger and needs their help. Unwilling to trust him, Ashley is uncooperative. In an effort to persuade her that his intentions are sincere, he discloses startling information about her mother that leaves Ashley reeling.
Although separated with no means of contact, Magnus, Will and Ashley must each figure out who to trust in order to link back together.