Darien Fawkes is a con-man and thief who is captured for a third time. Rather then face California's three-strike law, he volunteers for an experiment conducted by his brother Kevin. Kevin and another scientist, Arnaud, have created a synthetic gland that secrets ""Quicksilver"", a substance that can bend light. They place the gland in Darien's head. He soon realizes what has happened and is none too pleased. Darien is even less happy when they discover the gland secretes Quicksilver into the recipient's brain, and enough of it drives the person insane. Darien learns to control his abilities, and soon discovers that Arnaud is up to something. Arnaud claims Darien is insane when he accuses the scientists, but then Arnaud's mercenaries break in, steal the information on the gland, and kill everyone except Darien. Darien goes to his ex-girlfriend, a doctor who is furious at him because he didn't reveal his past. She refuses to believe he can turn invisible, and then Darien is taken away by

Going to Mexico to investigate Arnaud, Bobby meets his new partner Bobby Hobbes: a veteran spy and near basket-case. They escape an ambush by French-Canadian spies. Meanwhile, Arnaud has had Darien's girlfriend Casey brought down to Mexico, planning on using her as a hostage. Darien goes to rescue her, prepared to kill Arnaud since Darien thinks he'll be going insane shortly. Arnaud plays his trump card: there's a counter-agent that will stave off Quicksilver madness, and he'll give it to Darien if he works for him. Darien refuses, escaping with Casey and blowing up the compound (although Arnaud escapes). Both the counteragent and the formula are destroyed, and Darien goes to visit his brother's grave one more time before going permanently insane. However, the Official meets him there and reveals that his Agency was working with Kevin, and they have the counter-agent as well. As long as Darien works for them, he'll get regular doses of the Counter-Agent. Reluctantly, Darien agrees.

To bolster Agency funds, the Official comes up with a plan where he, the Keeper, and Hobbes will go to one of Arnaud's casinos and, using Darian's invisibility powers, break the bank. The first part of the plan goes well, but Darian decides to steal the remaining $7 million of the casino's money on his own. When confronted by the Official, Darian denies the theft. In response, the Official cuts off his supply of the counteragent. Arnaud contacts Darien and offers him the counteragent in return for the money. Stalemated with the Official, and with quicksilver madness coming on, Darien is tempted, but Arnaud mysteriously disappears. Darien talks with Arnaud's imprisoned brother Huiclov, who refers him to a doctor that Arnaud was visiting. darien goes to the hospital to the doctor, already red-eyed with madness. The Official has sanctioned an outsider to bring in Darien, taking an unhappy Hobbes off the case. Hobbes tracks Darien to the hospital on his own, and manages to find him with a

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.