Having traveled through interdimensional rifts in order to neutralize the threat of Adam Blank - the inspiration for Dr. Jekyll and Mr. Hyde - has given Helen a nasty case of radiation poisoning. Perched on the brink of death and knowing that Adam holds the key to his own salvation as well as hers, she has no choice but to share the dark secrets of the Sanctuary's origin with Will. She slowly unfolds their history: their studies at Oxford, Adam's wish to be a part of the experiment with the vampire blood, and his rejected plea for such.
But the hardest part comes years later: Adam's daughter was dying of a rare blood disease. Knowing that Magnus was a pioneer in this field, Adam sought her help, which she gladly gave. But the girl was too ill, and Magnus was unable to save her. In his grief, Adam twisted the facts of the story to make himself believe that Helen had refused to help. His continued rage over his daughter's death gave birth to the split personality he bears, and caused him to terrorize London. It was this threat to society that pushed the Prime Minister to contact Helen and her cohort, promising clemency for Druitt, a blind eye to Tesla's unorthodox experiments and full support for Helen's research with abnormals - providing The Five could track down and kill Adam. Though reluctant, the incentive was too strong, and when they discovered that Adam planned to poison the whole of London, Helen and her colleagues decided they must do as the Prime Minister wished. They tracked him down to an excavation site, where Helen fired a warning shot into his shoulder just before he jumped off a cliff into a river below.
All of this new information sends Will into a tailspin: he's been batted around by Adam, who insists that the only way to save himself - and Magnus - is to travel to the underground city, Hollow Earth, while also feeling betrayed by Magnus, who kept such a huge secret for so long.
Raising the stakes, Magnus - on Adam's instruction - has recovered Druitt from his Philippine hideaway, thinking he may be able to shed some light on how Adam survived a deadly fall, and how he has managed to live for so long. All Druitt can offer is the information that he materialized just in time to catch Adam before he hit the water. Adam offered his final resources - which would prove able to keep the secret of The Five for the following eighty years - and beg to be let go. Druitt, seeing the gunshot wound sapping the life from Adam, believed he didn't have to kill him outright - he could simply let him die. Druitt let Adam drift away in the river, but that river took him to a place no one could have imagined: Hollow Earth. There, he was healed, and learned secrets of humanity that dazzled them all.
Now, he's demanding to go back, with Helen's help. When she refuses, Tesla enters with an alternate plan. According to the Sanctuary ledger, if the head of a Sanctuary is compromised, as Helen is, command goes to the second officer. And with that swift curveball, Tesla turns the decision of whether Adam gets to see the city over to the unsuspecting Will.