Donna Stone is an agent with Acme Industries.
More specifically, she is an assassin for this ultra-secret organization in America's Intelligence Community. Acme is actually one of several CIA-sanctioned subcontractors which exist so that certain tasks deemed vital for national security can get done and when Congress asks about it, the Agency can go all holier-than-thou and truthfully (well, sorta) avow they had nothing to do with it.
When first we meet the resourceful and soon-to-be deadly Ms. Stone, she imparts to us via a preamble to the first chapter in that recorded adventure: "Any woman can be both the perfect housewife and an accomplished assassin, because both functions require the same qualities: creativity; a never-say-die attitude; and an attention to details, no matter how small..." She starts the actual chapter with these words of explanation: "All I really needed to know about being a freelance assassin I learned before my youngest daughter, Trisha, started kindergarten."
Stone is the proud mother of three children, Mary who is 12 and according to her mom a first-class flirt (just like her mother, Stone admits). Then there is Jeff who is 10, much into sports and a frequent pain in Mary's neck as all younger brothers should be. And Trisha who is in kindergarten.
Stone is a single mother because her husband, Carl, is, to some friends and neighbors, always away on business and to the children has run off with another woman some time back. Stone knows the truth, though, which is that Carl is dead, killed working in a business she had no idea he worked in when she met him, fell in love with him, and then married him. The now deceased Carl was an agent with the CIA, something Stone found out "five years ago, on the evening he was murdered". That date was also the year the youngest was born.
And Stone makes ends meet by working as a paid killer for Acme which when we meet her is also how she hopes to someday avenge his death. As she puts it, "each hit takes me closer to the bastards who took him away from us. At least, that is what I tell myself".
As the series progresses we will learn more about Carl (none good) and lots more about mixing single parenthood and assassinations, not the most common of pairings. We will see a good amount of changes in the lives of all involved but we will always keep seeing Donna Stone in some incredibly bizarre and usually hilarious situations.