After Mighty Mouse & the Mighty Heroes was cancelled in 1967, Terrytoons was unable to sell another series to CBS or anywhere else. Oh, Heckle & Jeckle would later return in rerun form as a mid-season replacement on NBC in the early 70's before settling into syndication, as would Deputy Dawg, but the studio was pretty much done.
Undaunted, producer Bill Weiss forged ahead, and continued to move away from the funny animal characters that were Terrytoons' trademark. Capitalizing on the spy boom of the period, Weiss, aided by animators Fred Calvert and Iwao Takamoto, among others, tried selling a pilot featuring teenage secret agent Sally Sargent.
With Ralph Bakshi having left Terrytoons (he was working on Spider-Man at the time), the end result was a decidedly un-Terrytoons look that more closely resembled Hanna-Barbera's adventure output of the period, especially considering Takamoto was working there at the time, too. Gary Owens (Space Ghost, Rowan & Martin's Laugh-In) narrates and doubles as agent Blake Jameson. Janet Waldo voices Sally, and I believe her boyfriend's voice belongs to Tim Matheson (Space Ghost, Jonny Quest, Young Samson). Cartoon historian and expert Jerry Beck, through Cartoon Brew, uploaded Sally Sargent to YouTube:
Nearly 35 years later, there would be a female secret agent appearing on Saturday mornings---Kim Possible. I don't think Kim would've gotten very far if her creators hadn't been aware of the existence of Sally Sargent.