For one of Stableford’s August Dupin stories, the plot here is fairly simple. As the title suggests, there is also a lot more scientific speculation in this story than others in the series. But, as usual in these books, Stableford hangs multiple meanings on his title. Here it is not only the evolution of life as a whole but that of a single human.

Fittingly, we get some back stories on our main characters.

Our narrator, unnamed thus far in the series, is Samuel Reynolds. Hardcore Edgar Allan Poe buffs will recognize the name as part of Poe’s delirious utterings as he lay dying. At novel’s end, Reynolds makes an interesting statement: he wishes he wouldn’t have made notes on the whole experience. He really doesn’t like being reminded of it. As with “The Legacy of Erich Zann” and, to a lesser extent, The Quintessence of August, Reynolds seems to have a protective amnesia about his experiences.

And Dupin’s early life is also revealed.

It’s the spring of 1847, and political tensions are high in France.

Dupin and Lucien Groix, the head of Paris’s police and another frequent series character, hung about the salon of Achille Maret when they were young. They were both in love with the beautiful, teasing, manipulative Julie, Maret’s daughter.

She’s still beautiful twenty years later when she turns up again in Paris. She is now Julie Guérande, her husband Claude is also a former member of that salon and friend of Dupin. She approaches Reynolds to get Dupin to visit her place in the Ardèche. She’s worried about her scientist husband’s obsessive interest in the mystery of some local caverns. He has been looking for something in them for the last 20 years. And it seems he has at last found it, but he won’t say anything about to Julie despite her being pretty well educated in science given all she heard in her father’s salon.

Dupin agrees to pay Claude a visit. He’s curious to learn what he’s been doing. And Groix wants him to attempt to diffuse a brewing political conflict in the area. The tottering French republic doesn’t need any more problems.

There is a nomadic tribe that returns to the area around Ardèche every summer. They are the Thiearchians, and they have a bad reputation. No, they aren’t accused of human sacrifice or cannibalism. But they are suspected of being behind the many disappearances of local children. The validity of Guérande’s title to his land faces some legal challenges in the confusion following the French Revolution of 1789. The Thiearchians and the Church are interested parties in the case.

The Thiearchians have an unusual mythology about some alien beings who live in the caverns of Mount Dragon. Into this Stableford brings the evolutionary ideas of Benoit de Maillet and his Telliamed. (His author’s note also states that the Thiearachians were inspired by Jean Richepin’s L’Aile, translated by Stableford and published as The Wing by Black Coat Press.) Dupin and Reynolds will encounter those aliens and their vast cycles of time will have echoes in the shorter lives of some of the characters.

In some ways, I liked this novel the least of the Dupin series probably because it forsakes discussion of music, literature, and the occult for something more scientific. On the other hand, it was nice that Stableford revealed more of his main characters’ pasts. And the ending definitely makes this an interesting work of science fiction. ( )