Geraldine Husk is the founder and administrator of the fake security agency SPI (Super Protection International), a rival to WOOHP. In "S.P.I.", SPI agents continually managed to capture various international criminals before the WOOHP even arrived at the locations. This brought positive publicity to SPI and make WOOHP appear ineffective. Beverly Hills High even held a "SPI Appreciation Day" festival complete with promotional merchandise. WOOHP was then shut down and replaced with SPI.
Investigating SPI further, Sam discovered that the "international criminals" SPI had been capturing were in fact employees of SPI. All of the criminal incidents had been set up by Geraldine in order to build up SPI's public image and discredit WOOHP. Geraldine had started SPI to get revenge on WOOHP. When she was a teenager, she had applied at WOOHP, but had been rejected, causing her to seek revenge. The girls managed to defeat their SPI counterparts and stop Geraldine's plan to loot the federal banking system.
After her initial defeat in "S.P.I.", Geraldine developed a personal vendetta against Clover, which is seen in two of her future appearances. She also sets up base on gargantuan ship that resembles an island. Which is used in later episodes as well.
In "Super Agent Much?", Geraldine returned with a scheme to secretly modify Clover into a super spy. As a result of Geraldine's secret modifications, Clover slowly became much more competent, demonstrating nearly superhuman abilities. The cost was Clover also became much more aggressive and sociopathic, preferring to work by herself, citing that partners would only slow her down. Geraldine ultimately recruited the modified Clover into SPI, and ordered her to kill her friends and to destroy WOOHP.
Clover's modifications turned her into a bionic woman (complete with laser eyes) and despite her best efforts including her newly designed weapons, she was defeated by being thrown into a lake via a electromagnetic Gadget. Geraldine was captured shortly after, and Clover was returned to normal.
In "Arnold The Great", she initially tried to lure the girls into a trap, but Arnold Jackson activated the trap instead. Changing her plans, she manipulated Arnold into joining her team and used him to trap the spies. However, Arnold was the one who ultimately stopped her, by clogging her vehicle's exhaust pipe with his Gummy Snare Blaster. She vowed to take revenge on him.
In the Blaine arc in Season 5's "Return of Geraldine", Geraldine is revealed to have hired Blaine to kill Clover. Upon Blaine's failure, Geraldine arranges a series of events in order to have Clover's entire life turned upside down, and everyone turn against her. With Clover left with nowhere to go, Geraldine uses Blaine as a decoy to capture her, and then attempts to kill them both. However, she is once again defeated and imprisoned.