Leon Garfield has said that we are all the ghosts of what we were. Unfortunately, if we are to afford Garfield the level of critical response his remarkable achievements demand, it must be acknowledge that [The Prisoners of September] echoes uncomfortably the stylistic brilliance of earlier works without developing into significant, fresh areas.
It is as if he is drawn spectre-like to the scene of previous triumphs. The characters are disconcertingly recognisable, patchwork creations from the dramatis personæ of earlier novels, while the relationships too explore familiar ground—the love-lorn boy drawn irresistibly to the blood-sucking woman for instance.
I hasten to add, however, that second-class Garfield is far in advance of the generality of writing for children. Perhaps the core weakness of The Prisoners of September lies in its construction, unlike his other books, around a specific historical event, the French revolutionary September massacres. This has forced upon the author a particular 'political' position. So, what had in Smith and Black Jack seemed a rich recognition of the complexity of human nature and the interdependence of human beings, here appears a slightly cynical, distanced observation of human motivation.
Adelaide Harris shared this tone but being much more broadly comic, it succeeded. Now we have a somewhat tired repetition of the unique style, presenting a disillusioned liberal-humanist world view. (pp. 244, 247)
Gordon Parsons, in The School Librarian, September, 1975.