At the Sanctuary, Magnus briefs the team on a series of attacks in which abnormals are viciously assaulting humans. The unprovoked pattern of violence seems to follow the air stream indicating an airborne virus or biological agent that incites aberrant behavior. The team is not certain if this is a natural occurrence or intentional biological warfare.
Before long, an unwelcome John Druitt arrives at the Sanctuary with information that the Cabal is behind the infectious outbreak of violence. At the same time, Dr. James Watson, another member of The Five and head of the UK Sanctuary, contacts Magnus. Watson further substantiates the Cabal's involvement.
Although they are now exposed to the potential cause of the outbreak, Magnus, Druitt and Watson do not appear to be affected. Magnus deciphers that an antigen found only in the blood of The Five likely protects them.
It stands to reason then, that if the blood of The Five renders them immune to the deadly pathogen, then the Source blood from which they were all injected may be the key to protecting other abnormals from the disease.
But the only remaining vial of Source blood has been hidden and protected by Magnus's father in a labyrinth under the lost city of Bhalasamm in India. There, five keys are concealed, each retrievable only by the unique powers of The Five.
Although Magnus, Druitt and Watson are already gathered, the team has no way of finding the two remaining members of the group. After her last encounter with Nikola Tesla in Rome, Magnus is unsure if he is even alive. And the fifth member of the elite group, Nigel Griffin, died half a century ago.
Knowing that her father always planned one step ahead, Magnus is convinced of the stringent measures he applied to allow for such an event. She explains to the team that it is not each original member of The Five that they need for this task, but rather, each of their unique powers. Understanding this, they realize they must find someone who also possesses Griffin's special gift and that person is none other than his own daughter.
Henry is able to locate the last known address for Griffin's daughter Anna, but then he also discovers that she has been dead for three years. There is evidence to suggest that she may have faked her own death so Druitt and Will set out together to find answers in hopes of bringing Anna, and her critical gift, back to the Sanctuary.
Meanwhile, Ashley and Henry are convinced that assembling The Five is taking too much time while the Cabal continues to prepare its assault. They propose a visit to the Cabal's weapons factory where they can shut down the operation at its heart. Without the specially designed dispersal device, the Cabal has no means of spreading the infection.
Although reluctant to let her daughter go on such a dangerous assignment and worried about Henry being able to handle the task with such little field experience, Magnus agrees nonetheless, realizing they need a back-up plan in case they are indeed unable to retrieve the Source.
As the Sanctuary team prepares for their missions, their suspicions are confirmed; the first outbreak of abnormal violence was just a trial run. In three days, the Cabal intends to initiate an attack that will be catastrophic for the delicate balance between abnormals and normals, and threatens to reshape the world as we know it.