Take the vanishing Lord Lucan, add an impostor who may or may not be in cahoots with the missing earl, stir in a respected Parisian psychotherapist with a dark secret of her own who is treating both men (and being blackmailed by them), throw in a pinch of African tribal chief, a soupcon of ambitious Lucan biographer, sprinkle liberally with the psychotherapist's motley crew of patients, and what do you get?
A novel with the fictional density of a good minestrone soup, you would think. The bad news is that the minestrone's off and the reader has to be content with a tepid consomme.
By shunning this rich fictional mix, Ms Spark evidently did not want to write a psychological exploration of, or a morality play about, Lord Lucan who disappeared in November 1974, after allegedly bludgeoning to death his children's nanny, the unfortunate Sandra Rivett, whom it is thought Lucan mistook for his wife.
Lady Lucan, who happened upon the murderous scene, was also attacked with a blunt instrument and almost choked to death before the intruder made off into the dark - and into obscurity.
Well, relative obscurity. For though the missing Earl has been officially declared dead, he has been "sighted" in various European hotspots, and further afield, over the years.
Spark's contention - evident from the title of the novel - is that to survive all these years Lucan (and by extension, all bounders, fakes and impostors) must have enjoyed the collaboration of a close circle of friends who dished him out money and kept his location a secret. She imagines a freemasonry of like-minded upper-class compatriots who see no moral dilemma in supporting a declared murderer on the run.
Spark does not judge them - or Lucan - she sends them up. "Even if Lord Lucan had not been a cold-blooded killer, I could never have liked him," Spark has said about this novel, her first in five years. "But my researches provoked a desire to ridicule the man, rather than thoroughly condemn him. I had fun with my imagination."
This is the woman who famously gave us the zany, irrepressible and thoroughly wrong-headed Miss Jean Brodie; what a pity she couldn't have had the same fun with Lucan. He is by her account a dull and limited man. Someone deeply lacking in imagination, as indeed all would-be killers must be. Okay, so Lucan is a dead loss, but what about Spark's heroine, the psychotherapist, Dr Hildegard Wolf, formerly Beate Pappenheim, a stigmatic impostor and fraudster, who as an impoverished medical student swanned around Munich, bleeding at will, embezzling Catholic funds ("more money in Irish currency than any other was found to have been placed to her account") and even prompting a few miracle cures? Surely, the reader could expect to get some mileage out of her? And the plot, you would think, might thicken when within weeks of "Lucky" Lucan turning up on Dr Wolf's couch, a second man, also claiming to be Lucan, shows up to be analysed.
There's a certain slapstick quality to all of this. Think the Three Stooges as the impostors busily trail one another about, the hunted becoming the hunters. Or recall Dick and Jane go on a big adventure, as two amateur sleuths set off to find the Lucan doubles and keep on bumping into them unawares, first on a flight to Paris, then as Father Christmas in a Parisian department store. And imagine the Boys' Own for the finale in Africa in which one of the impostors meets an all-consuming end. But Spark's writing strangles the humour at birth. The prose reads like a stilted translation, the black comedy veers about without a focus. Who is it exactly we're supposed to be laughing at? Muriel Spark may well have written Aiding and Abetting for laughs, but it's a mirthless trial to read.
Mary Morrissy's most recent novel The Pretender was published earlier this year by Jonathan Cape