Originally working as a MetroPol Motorpool records officer, Frankie has desperately wanted to join the Viper Project ever since he found out about it, and has been constantly asking the head of the project, the car's inventor Julian Wilkes to sign the transfer papers. However, Wilkes has constantly denied him, which really upsets Frankie.
However, after Councilman Strand cancels the Viper Project, Frankie reveals the Viper's driver, Joe Astor, that he found out that Strand was bribed by the Outfit to cancel the project and destroy the car. Frankie and Joe then steal the Viper from the garage by pretending to be taking it to the crusher. In reality, Joe, at gunpoint, hijacks the Viper and forces Frankie out of the car, to protect him from any future reprimand.
Later on, Frankie finds out that Joe has used the money taken from Michael Payton's account to buy an abandoned power station and set it up as the team's safehouse. He then shows up at the safehouse, and again wants to be part of the now-independent project. Wilkes finally agrees.
Frankie would work with Joe and Wilkes through the season as the team's MetroPol insider. After MetroPol takes over the project, Julian takes a post in Washington, DC and Joe leaves for Thailand, Frankie stays on with the project as the team's mechanic, as a new team is assigned - Thomas Cole as driver, Allie Farrow as systems designer and Cameron Westlake as the MetroPol liaison, later on also Sherman Catlett as FBI liaison. After Allie leaves to work for a government think-tank in Portugal, Frankie would take over her duties as well.
During Seasons 2 and 3, Frankie is now seen sporting a goatee.
In Season 4, now again sporting his clean-shaven look, Frankie is the only one currently remaining of the Viper project after the Viper was destroyed to prevent it from falling into enemy's hands, Cole being permanently reassigned and Westlake being transferred back to MetroPol. With Metro City being gripped by another crime wave, Frankie and Catlett are trying to find a new driver, and Frankie even volunteers to drive himself, only for the car to get blown up (and himself to get ejected by the ejector seat). Later, Frankie mentions to Westlake that he knows one man who could handle the Viper - Joe Astor, albeit he hasn't seen him for three years.
As Joe arrives to deliver the new Viper as a favor to Julian Wilkes, and has been subdued by Westlake, thinking he was an intruder, Frankie sees him and annoyedly informs Westlake of his identity, before he and Joe hug, having met again after many years.
Waiting for Wilkes to arrive, Frankie, Joe and Westlake decide to check out the new Viper, Frankie attempts to convince Joe that they need a new driver, but Joe informs him that he has another plans. After discovering that Wilkes has been kidnapped, Joe and Westlake head out in the Viper, with Frankie assisting them from the Viper's base.
After Wilkes and Catlett have been rescued, Frankie, Joe and Wilkes are seen in Catlett's office, as Frankie mentions that it's good to have the original team back together. However, Wilkes says that having taken an offer with NASA, he won't be staying with them, and Joe again reminds him he has another plans. Frankie is dismayed that "It's just gonna be me, Franklin X., all alone against the horde?", just as Westlake and Catlett walk in. However, Wilkes informs Joe that he has suggested to FBI to take Joe on as the driver and reassign Westlake to the team. Joe is still reluctant, but Frankie convinces him that the Viper project needs him, and Joe finally agrees to stay.
During Season 1, Frankie's common catchphrases included "Poke out my eyes!", "Can I tell ya somethin'?" and occasionally "It's the principle of the thing."