Dr James Courtney uses plastic surgery to transform his secretary, Lisa Galloway, into a double of Jaime to infiltrate the OSI and steal top-secret information. After two weeks of training in Jaime's mannerisms, voice, and life history, and also in killing Oscar with poison darts by using a cardboard cut-out of him as target practice, Lisa is confident she is ready for action. But there are still three key differences between Jaime and Lisa. The first is, of course, Jaime's bionics, which they do not know about. Second, Lisa smokes while Jaime does not, and her smoking habit keeps filtering through her Jaime impersonation. Third, Lisa has a Southern accent as she hails from Georgia.
Lisa heads out to the OSI. Oscar is surprised as Jaime is supposed to be on vacation in the Bahamas. Lisa manages to cover up and wangles her way to Oscar's top-secret paperwork of a vital document, the Howlett Report, of which she takes photographs. At the Pump Room bar, Lisa passes over the information to her contact, Matthews, and is sent back to the OSI for more.
Meanwhile, Courtney has his henchman Baxley intercept Jaime at the Bahamas, where they try to kill her by drugging her, throwing her in a crate, and dropping her in the sea. Jaime breaks out with her bionics, but Baxley gets away. She swims to shore and phones Oscar about the attack – just at the precise moment when Lisa is back in Oscar's office. Realizing she has been detected, Lisa tries to kill Oscar with her darts, but he ducks and the dart goes into his chair instead. She is arrested and held in custody while Jaime is recalled to the OSI and confronted with her.
Oscar realizes Lisa what top-secret information Lisa has passed on, and it is critical they retrieve it. But Lisa refuses to talk, so Jaime poses as her, and uses their only clue – a matchbox from Pump Room in Lisa's bag – to attempt to find her contact. After a long wait (and a lot of drinks) she makes contact with Matthews. She tells him that she has information, but it is in her head and she needs to speak to the boss personally. She manages to wangle her way to Courtney's office with Matthews. Oscar's surveillance is on the trail, but he loses her in the traffic. He phones Oscar about it. Lisa is in earshot and suspects Courtney's clinic is in danger.
Jaime and Matthews arrive at Courtney's office. Jaime soon learns that the top-secret information is in a vault in the basement. Her impersonation of Lisa runs into trouble when she is expected to smoke when she does not, and they also say she can talk like herself, but she does not know what Lisa is supposed to sound like until Lisa's boyfriend Perkins points her in the right direction. Jaime then affects a convincing southern accent, but has to put up with Perkins's smooching all over her in a basement where the Oscar cut-out is stored. Soon she meets Courtney himself, who seems suspicious, especially after she tries to smoke, and her stalling tactics make him more so. He tests her by directing her to open his safe, which she manages to do with the help of her bionic ear. Courtney seems satisfied, and is then called away to intensive care. But Jaime bionically overhears Courtney telling Matthews that Lisa is acting strangely; she is not to leave while Perkins is not to get in, and his phone line is to be disengaged while he is out of his office. So Jaime cannot phone Oscar for help.
Meanwhile, Lisa escapes from the OSI with a gas bomb disguised as a lipstick that Courtney gave her and makes her way to Courtney's office. But she has taken a cab to get there, and Oscar's men overheard her direct the driver to Courtney's clinic. So Oscar and his men are now making their way there with all speed.
Lisa arrives at Courtney's surgery, and Jaime bionically overhears her confusion when she hears that she is in Courtney's office. Jaime bionically escapes Courtney's office and sneaks back into the clinic while Lisa goes to fetch Courtney. This causes more confusion for the villains until they finally catch on. Now they are after Jaime.
Jaime is back in the basement with the cut-out, and wishing it was the real thing. Baxley arrives in the basement and tries to kill her again, but Jaime deals with him bionically. Courtney and Matthews try to head for the basement as well, but are apprehended by Oscar and his men.
Then Lisa herself arrives in the basement. She tries to kill Jaime with her poison darts, but Jaime uses her bionics against them. Oscar arrives, and does not know how to tell them apart. To enable him, Jaime is forced to demonstrate her bionics, although this means giving her powers away right in front of Lisa. Upon seeing this and Jaime not being dead after taking an armful of poison darts in her right (bionic) arm, Lisa admits defeat over ever being a real Jaime impersonator.
They recover the stolen information, and find a whole lot more in Courtney's vault. Surgery to restore Lisa's original appearance cannot be performed for a year because of scar tissue. So she is going to prison still looking like Jaime, and Oscar can only hope she will remain there until the surgery can be done. Jaime is chagrined to be stuck with a prison inmate for a double, and also at Oscar's apparent lack of sympathy for her about it. She gets her own back on Oscar with a practical joke, using the cardboard cut-out of him from Courtney's surgery.