Our book today is 1982′s mystery novel Light Thickens, the last book written by the great New Zealand mystery author Ngaio Marsh (by far the most deceptively cerebral of the four “Queens of Crime”) before she died in harness that same year at the ripe old age of 86 (ripe and hypothetical, since in the time-honored tradition of British ladies of letters, there’s some debate over the correct year of her nativity). The book therefore certainly qualifies (even morbidly puns) as late style, but you’d never know it from the work itself, which is as sharp and intelligent and pleasingly wry as anything the author had written in the previous fifty years. Partly this evergreen quality was the luck of literary inspiration (other writers have had it too, although it runs particularly strong in genre masters, for obvious structural reasons), but mostly it was the product of Marsh’s iron self-discipline and the fact that she was her own fiercest critic. She wrote finished prose at breakneck speed, but she was even so a ruthless pruner and discarder.

Her first artistic love, famously, wasn’t writing at all but the theater; she worked all her life to bring competent stage productions to her benighted, earthquake-ravaged homeland, and with considerable success. And her theatrical passion is amply represented in her crime fiction – the theater is the setting for half a dozen of her thirty-two novels, including (as is obvious from the title, and also from the great Alexander Farquaharson cover-illustration for the Book Club edition of the US hardcover) Light Thickens, which has a central gimmick as sleek and enviable as virtually all of Marsh’s gimmicks were (something that most definitely can’t be said for her three fellow queens): in a production of Macbeth directed by Peregrine Jay for London’s Dolphin Theatre, the raucous sword-play that concludes the final act ends with Macbeth’s severed head stuck on the blade of a gigantic Highland sword called a claidheamh-mor (Star Trek fans will know the weapon from a scene I need hardly identify) – only the head on the sword is real.

Beautiful.

A thoroughly shocked Peregrine Jay is in the audience and watching when the whole thing happens, and so, as chance would have it, is CID Chief Superintendent Roderick Alleyn of Scotland Yard, the passionate, dedicated hero whose career is traced through all of Marsh’s novels. He and his indefatigable assistant, Inspector Fox, immediately set about investigating the crime, but one of the most memorable parts of Light Thickens – one of the surest signs of its author’s sheer mastery of what she’s doing – is just how much of the book isn’t about the murder at all. Chapters and chapters are devoted instead to Peregrine Jay’s efforts to inspire the cast and shape up the production, and it’s all so fascinating that even the most bloodthirsty reader wouldn’t have it any other way. All throughout Marsh’s later life, friends and correspondents routinely urged her to write a book about staging Shakespeare – many of them had experienced first-hand how beguiling she could be on the subject, and they didn’t want all those incredible insights lost to theater lore. She never wrote such a book (that we know of – again, in the time-honored tradition of British ladies of letters, she did nothing in her lifetime to squash rumors of unpublished manuscripts), but some hints of it can be gleaned from her murder mysteries. The stage-centered ones abound with shrewd insights into the craft of doing Shakespeare, as when Peregrine Jay talks about the particular demands of the scene where Banquo’s ghost appears to Macbeth:

“If ever there was a scene that could be ruined by a bit-part actor, this is it. It’s all very well to say you must completely ignore the ghost, that for you it’s not there; it’s hellishly difficult to do it. If you can actually look at it without focusing your eyes, that’s fine, but again it calls for a damn good actor to achieve it. We’ve got to make the audience accept the reality of the ghost and be frightened by it. The most intelligent of you all, Lennox, has the line: Good-night; and better health attend his majesty. When next we see Lennox he’s speaking of his suspicions to Ross. The actor will, every so slightly, not a fraction too much, make us aware of this. A hair’s-breadth pause after he says Good-night, perhaps.”

Once the murder investigation is under way, Alleyn and Fox face no shortage of suspects – and theater folk being just a wee bit egotistical (they tend to want the starring role in everything), each one of them thinks official suspicion is resting mainly on themselves. It’s an impression Alleyn, in his typically candid way, is quick to contradict whenever anybody says, “I’m your prime suspect, aren’t I?”:

“To be that,” said Alleyn, “you would have to have pulled off the dummy head and used the claidheamh-mor to decapitate the victim. He would have to have waited there and suffered his own execution without raising a finger to stop you. Indeed, he would have obligingly stooped over so that you could take a fair swipe at him. You would have dragged the body to the extreme corner and put the dummy head on it. Then you would have put the real head on the end of the claidheamh-mor and placed them both in position for Gaston Sears to take them up. Without getting blood all over yourself. All in about three minutes.”

Simon stared at him. A faint color crept back into his cheeks.

“I hadn’t thought of it like that,” he said.

“No? Well, I may have slipped up somewhere but that’s how it seems to me.”

Of course the key to Golden Age protagonists – and Alleyn is a pure specimen if ever there was one – is that they rarely ever really do slip up somewhere. Alleyn certainly doesn’t in Light Thickens, despite some very enjoyable (and skillfully deployed) early confusions. Marsh’s one main weakness as a mystery writer (also a bleed-over from the theater world, if you think about it) is her tendency to telegraph her culprits, and that happens true to form in this last novel as well. But it hardly matters – it’s all so deliciously done that no sane reader will care. Instead, they’ll have a walloping good time and then re-read the thing ever other year, as nature intended.