After the recap scenes, we see a large, alien-looking jet with bent wings flying over a snowcapped mountainous region. A bomb is jettisoned into the snow below. Suddenly there is a large explosion which releases an expanding greenish cloud. Next, a lone abnormal with a strange pig, or perhaps walrus, face is chopping wood in the forest when suddenly he is infected by the gas. He gasps, falls to his knees and passes out. Elsewhere, a man and a woman are tending their garden when the walrus man stumbles out into the clearing. The man, George, is startled but relaxes when he sees who it is. "Roy," he calls out to his good friend. But Roy, who is holding an axe, is staggering and grim-faced. Suddenly he lunges at his friend with the axe and the woman screams.
Dr. Magnus, Will, Henry and Ashley are looking at a computer screen in the Sanctuary's library, going over reports of "sudden unexplained violent behavior among abnormals." The reports, starting in the north, seem to be "following the upper air stream" as they spread south. Magnus declares that they have to find out if this is a naturally occurring phenomena or an intentional act. The Big Guy answers the door only to find John Druitt standing there. Although he doesn't want to let him in, Druitt has an opening : "I bring critical information, my hirsute friend, about the troubles in the north."
Magnus is unamused : "Forgive my skepticism, John, but your history of altruism is just behind a scorpion's." Ashley shows him no respect either. When he protests that he is her father, Ashley replies that perhaps he "should start acting like one, and that does not mean kidnapping me when you want to spend some quality time." Druitt opens the large black bag he has been carrying to reveal the charred remnants of a dispersal device which he recovered from ground zero of the explosion. Magnus, suggesting he's a possible bio-hazard (and not trusting him one bit), wants him locked up in "a level-three residential cell" with an EM shield so that he can't teleport out. When Ashley questions his motives, Druitt tells her "The war has begun. Humans versus abnormals, and I will not stand idly by while the Cabal imposes its chaos."
Although he has only begun his study, Henry reports that the device is highly sophisticated, like "stuff they used to test at Fort Dietrich for defensive purposes." The Big Guy brings in a telegram from Dr. Watson, the head of the U.K. Sanctuary. Watson will be arriving tomorrow. Will is flabbergasted that another member of the Five is still alive. Elsewhere, Whitcomb is walking thru a Cabal building, being briefed by an unnamed scientist on the great "progress" of the outbreak. Although the poison will wane in four days, she is pleased with the results of the test : "The reaction to the abnormal uprising is exactly what we hoped for. Anger, scapegoating, retribution. That's your real vector of transmission." Whitcomb confidently dismisses a colleague's concerns about The Five, saying "they have no idea what they're facing." Nevertheless, she has ordered hourly updates on every communication "in and out" of the Sanctuary.
Dr. Watson arrives bearing "gifts" - a truckload of abnormal corpses. He greets Helen, Ashley and Henry warmly, but he studies Will studying him. "The protégé," he purrs. "Profiler, right?" "And people tell me I sound like Sherlock Holmes," laughs Dr. Zimmerman. "Actually, Will," replies Magnus, "that's exactly who he is." Later, Helen explains that Watson insisted that Sir Arthur Conan Doyle portray him as the bumbling sidekick in his stories. But Will is more concerned that Helen and the whole crew could become infected, psychotic and aggressive : "I've done that dance with you once, a half a mile under the ocean. I'm not anxious to do it again." Magnus and Watson perform an autopsy on a walrus-human abnormal, after which, in the lab, the quasi-crippled Watson regrets that they don't see enough of each other. Helen announces that she's released Druitt. "Now if you could only release yourself," replies Watson. "Most people go back to their oldest contacts for solace, Helen," he continues, "You defy that convention, but then again, you always have."
Later, in the study, as he adjusts his complex brace apparatus, Watson enjoys a brandy with Druitt and Will. The two old friends continue their centuries-old battle of wits. For Watson/Holmes, Druitt/Jack The Ripper was the one that got away, the case he couldn't crack. "Justice is meted out in many ways," intones Druitt, "you're not the only one haunted." They then toast each other. Henry is having trouble understanding the bio-dispersal device : "So much chop, so little suey." Then he finds an unexploded pure sample of the pathogen. Once the tests are complete, Magnus reports that the agent acts "like a prion on steroids." "The rogue protein found in Mad Cow disease," adds Will. Abnormals are driven crazy and made violent, only to die a very painful death. Dr. Magnus is convinced that something in the blood of The Five could be the basis for an antigen. If not, she argues, then perhaps the ancient source blood itself could hold the answer. Will is surprised to learn that some of the all the powerful source blood still exists. As it turns out, Helen's father locked the remainder away and only the Five, acting together, can retrieve it in an emergency. However, Tesla may be dead, and Nigel Griffin died half a century ago. Helen, however, thinks there may still be a way. Griffin told her that his powers had been passed on to his daughter. When Will asks what Griffin's power was, Watson informs him that he was the invisible man. Suddenly, in a hallway, the Big Guy collapses, bleeding from the mouth.
Helen hypothe that the microorganism may have entered the Sanctuary on Watson or Druitt's clothing. Henry fears that all the abnormals in the Sanctuary, including him, will become infected. As they watch their friend suffer, Whitcomb is again being briefed by the scientist. The Cabal knows that the Sanctuary has been breeched and infected. Whitcomb, however, is reminded that Helen's father didn't reveal the location of the source blood, which the Cabal clearly wants. Ashley's sources have reported that this was, indeed, a dry run; but that in three days, all hell will break loose. Helen is certain not having Tesla won't be a problem if they can find Griffin's daughter. Will is told that Gregory hid five keys needed to find the vial in the labyrinth located beneath "the lost city of Bhalasaam in the Indian Himalayas." Henry bursts in announcing that he has discovered the whereabouts of Griffin's daughter, who apparently faked her death, but they've got to hurry. They need Druitt to teleport there, but they don't trust him alone so Will is drafted : "What? Well, why me? I'm supposed to tell Jack The Ripper to fetch?"
The two of them find a girl in New Orleans who claims that Anna Thayer Griffin is indeed dead, which they don't believe. Meanwhile, Ashley is arguing with her mom to let her and Henry sneak into the Cabal's weapon's factory. "No offense, Henry," says Helen, "but you don't graduate from Eagle Scout to James Bond overnight." But she relents and let's them go. Will and Druitt are visiting the supposed gravesite when something strikes a branch. Will looks for footprints in the grass. They are tracking the prints when Will is suddenly kicked in the groin. Druitt wrestles with the invisible girl but she escapes. However, Will turns on the sprinklers so that they can see her and Druitt teleports ahead, capturing the shivering naked girl, Clara - Nigel's granddaughter.
As Will and Druitt try to talk Clara into helping them with their quest, the big guy begins going berserk, smashing everything in his sealed bio-room. He has a moment of clarity, saying "Helen, don't let me out" before the violent rage returns. While Magnus fumes about the Cabal, Will tells her that he isn't convinced Clara is up to it : "Look, she talks a tough game, but she's afraid of her own shadow, when she has one." But Will has a long talk with Clara, who says he sounds like her mother, and she starts to come around. Helen can't stand watching the Big Guy suffer so she goes in with him to try to save him. When he attacks her and she can't talk him down, she stuns him with a weapon.
Henry and Ashley prepare to sneak into the Cabal's factory, that is, if they can get past the barbed wire and lasers. Henry's device shuts off the lasers and in they go. Back at the Sanctuary, Helen is trying to keep Watson pumped as the five prepare for their departure. As Watson continues to voice doubts, Helen smiles and says : "Suck it up, Jimmy. We're going to India." At that moment, Henry and Ashley, having penetrated the building, are surprised, surrounded and shot with taser guns. They fall to the ground, unconscious. Druitt teleports the team to a forest outside the lost city of Bhalasaam as a frightened Henry, strapped into a strange chair, struggles to break free. Men in lab coats are all around him. "Who the hell are you," he demands. "Relax, Mr. Foss," says the scientist who has been advising Whitcomb, "I'm your Doctor."
Elsewhere, Ashley awakens to find herself alone in a lab room. She is untied, sitting in a chair which rests on a large metal surface. Touching the surface with her bare foot, she discovers that the it is electrified. She also finds that she has been injected with something. Whitcomb enters with two men. She apologizes to Ashley for the elaborate precautions, but says that her reputation precedes her. She also tells Ashley that, despite her efforts, 'Lazarus' will be released, and that its effects will be "a thousand times more devastating than phase one. When the dust settles," Whitcomb promises, "it will bring a new day for humans, and what's left of abnormals." She informs Ashley that her mother will fail because Ashley herself is going to help the Cabal succeed. Helen and the team reach the lost city only to find it totally destroyed. Watson is dispirited : "It's over. No access, no source. No source, no vaccine. No vaccine, no way to stop the Cabal from taking over human evolution." Things look grim indeed.