A young girl is a witness to an assassination by a sniper. Traumatized, she only speaks to her imaginary friend ""Ralph."" Darien, using his powers of invisibility, convinces the girl he is ""Ralph"" and tries to get her to talk about the murder. Eventually the hit man tries to kill the girl, and Darien manages to stop him. With his help, the girl starts to recover from her trauma, and leaves her ""imaginary friend"" behind.

The Official is forced to resign because of Darien's screw-up, and he and Hobbes have a new boss to deal with.

Darien is contacted by his former mentor and partner, Liz, who wants his help. She wants him to return to his thieving ways and help her steal some FBI files on a mobster who has hired her. Initially reluctant, Darien eventually grows aggravated with the Agency's treatment of him and links up with her. Covertly using his powers of invisibility, Darien manages to get hold of the files, only to realize that the mobster plans to use them to kill a government witness against him. Darien tries to thwart the mobster and keep Liz safe, and manages to do so. The two of them part on relatively friendly terms.

The Official is assault by an invisible man and Fawkes is suspected - Darien and Hobbes work to clear Darin and find the true assailant.

A ghoulish hitman uses a laser to blind any witnesses to his killings. Fawkes and Hobbes trace him to a blind model who the killer is romantically involved in, but the assassin escapes, blinding Fawkes in the process. Since he was turning invisible when the laser hit him, the effects are temporary, and he can still see if he covers his eyes with the quicksilver formula. Unfortunately, that aggravates his growing insanity. The blind model helps him to deal with his blindness, and the two become romantically involved. Fawkes figures out that the assassin's most recent victim was merely a lure to get his real victim to the man's funeral. Fawkes, overwhelmed by Quicksilver Madness, throws the assassin to his death.

Hobbes and Darien are on the trail of a sperm thief. A college professor is using the sperm to isolate intelligence-causing genes, and put them into a retrovirus. Hobbes is accidentally infected and soon begins to become more and more intelligent. But the partners discover that the gene therapy is lethal. Bobby becomes smart enough to create a cure...but refuses to do so, preferring to die smart then live dumb. Darien infects himself, leaving Hobbes no choice but to come up with a cure to save his friend.

Hobbes and Darien meet with one of Hobbes' contacts to set a trap for their arch-enemy, Arnaud. Arnaud manages to escape Darien with the aid of a smoke canister, which turns out to contain a biological weapon. Darien is soon displaying flu-like illness symptoms, and is excreting black, contaminated Quicksilver. The Official and the Keeper send him to a military hospital...which Arnaud has already infiltrated. He plans to remove the Quicksilver Gland from Darien's skull via surgery, but the illness complicates matters. He must kidnap the Keeper to cure Darien so he can gain an uninfected Gland. Darien manages to escape and, overwhelmed by madness, almost kills Arnaud. The Keeper manages to stop him but Arnaud escapes. (Copyright 2002 Steve Crow)

The agents find themselves hunting for the legendary Sasquatch on an Indian reservation after two men have been killed there under mysterious circumstances.

Darien decides to have himself injected with his brother’s RNA in the hopes that he can discover how to remove the Quicksilver gland from his head.

Darien loses his memory after being struck by lightning, and Arnaud convinces him that he is his own brother and that his Agency friends are really trying to kill him.

Arnaud seeks out Darien for help in exchange for a cure for quicksilver madness.

Darien learns that the Keeper and the Official have been keeping antidote secrets.