Billie - our main character and part-time narrator - tries to tamp down regrets about all the years she let work take precedence over a private life. Mary Alice is finding it harder to sustain her false cover stories to her beloved wife about her 'work trips.' Natalie, once a flirty 'gamine,' finds that her sexual stocks have fallen along with her boobs. Helen, whose 'refined' beauty once drew comparisons to Jackie Kennedy, is a widow stuck in grief.

Now in their 60s, their lives have been marked by change and loss. Raybourn's narrative toggles between the quartet's early exploits and the present, when their collective career is coming to a close.

Qualifying for an all-female squad known as 'Project Sphinx,' their job has been 'to eliminate people who need killing.' In flashback chapters, Raybourn (author of the Veronica Speedwell series) describes how the young women were recruited by a black ops organization known only as 'The Museum,' an offshoot of the OSS and its British counterpart, the Special Operations Executive. They rely on hypodermic needles laden with poison and, when things go awry, their own highly trained bare hands and a knife. Raybourn's story opens in 1979, with our four heroines on their first mission, posing as flight attendants on a private plane to carry out the execution of a Bulgarian bad guy and his henchman. Perhaps, one can hope, condescension to senior sleuths and spies is fading out of fashion altogether, given the success of Richard Osman's Thursday Murder Club series and the boomlet of mystery and suspense novels featuring older protagonists, including Ottessa Moshfegh's 'Death in her Hands' and the forthcoming 'Secret Lives,' by Mark de Castrique. Let's get all the patronizing comparisons out of the way because 'Killers of a Certain Age' by Deanna Raybourn - about four women who've reached the mandatory retirement age for professional assassins - is so inventive that the only ageist wisecracks it deserves are the ones its characters make about themselves. The Golden Girls toting Uzis Jessica Fletcher packing heat Miss Marple in the library wielding nunchucks.

Killers of certain age