This sister series to the Man from U.N.C.L.E. debuted in 1966, during the parent show’s third season. It was a development of a second season episode entitled “The Moonglow affair”. In this pilot story April Dancer is paired with an older, near retirement Mark Slate, who is resentful of working with someone as young and inexperienced as the newly trained Miss Dancer. April was to be played by, the 1959 Miss America, Mary Ann Mobley with Norman Fell taking the part of Mark Slate. While this pairing worked well, it was not retained, the parts instead being taken by Stephanie Powers and Noel Harrison.
Other major changes that took place between pilot and series, were that the character of Mark Slate was no longer an ageing agent assigned to look after a newcomer, but a younger British agent of the same generation as April, while April was no longer quite the vulnerable newcomer, but an independent capable agent in her own right. The series looked set to be an instant success riding of the back of big brother, but alas this was not to be the case, for all to soon the scripts began to rely far to heavily on the humour aspects of the story, a problem the Man from U.N.C.L.E. was also suffering from during this season. It was due largely to this much lighter format being adopted that it was decided to drop the show after its first season with only 29 one hour long episodes being made.