Eileen Merriman knows that if you are a teenager and you are given rules to follow by your parents, you’re going to break them. Within a couple of chapters lead characters Indigo Moon and Rigel Fletcher, between them, have broken both rules: 1. No shifting in public places; 2. No time-travelling. Like, ever.

If you are confused as to why these rules exist for these people, don’t worry, I was too. I have read two books in the Black Spiral trilogy, and while I had some idea what M-fever was and why the kids were called Offspring with a capital O, I certainly don’t remember any time-travelling.

If you have read the earlier trilogy—you’ll be on board from page one. If you haven’t, this may help: Offspring are enhanced humans. Their parents were the protagonists of the previous trilogy, which began with Violet Black. Rigel is Violet and Jonno (Black Wolf)’s son. Indigo is Bruno and Harper’s daughter. Rigel has a younger brother; Indigo is an only child. Their abilities include shapeshifting (‘shifting’) which includes the ability to travel to anywhere in the world and change into any animal; they can hear everybody think and see thought streams in colours; they can also time-travel.

Soon after the book begins, Indigo heads out to a club with her friends from 1996 London, where she locks eyes with a good-looking man called Billy Raven. Somewhat unwillingly and very unfortunately, she falls in love with him—he is very good-looking and something about his kisses makes her lose her inhibitions.

Meanwhile Rigel goes camping with his friends, who goad him into shifting. A moment of fun as he turns into a tiger leads into a tiger-hunt in a national park in Whangārei. While his parents read him the riot act, Black Spiral Intelligence becomes interested in him and sees him go to their base on a Helipod. In the meantime, his dad is off on a mission for Black Spiral Intelligence (BSI).

Rigel and Indigo used to be close and have a code they follow themselves—Offspring come first. An Offspring’s secret must be kept. An Offspring’s promise is binding. Until death. Rigel has some idea of what Indigo is up to but can’t tell anybody. It isn’t until after things go badly wrong that he has to get involved.

You can usually rely on Merriman to pull you seamlessly through her stories with a combination of clever writing and solid world-building but this time, I found I hadn’t been given enough of a knowledge base to understand the internal logic of the events that were happening to the Offspring. The pace doesn’t let up for long enough to explain things.

What Merriman gets right, though, is the complexity of being a teenager. Rigel wants to follow the rules but his abilities get out of hand, which leaves him in uncharted territory without his dad to set him straight (though he has Uncle Rawiri with him). Violet is a rebel who doesn’t think the rules should apply to her. And her first love seems like the only thing that matters at the time: ‘I laugh and let him kiss me, even though there are at least eight other people in the café. Euphoria-exhilaration rushes through me, so intense it’s as if I’m staring into floodlights.’

Merriman also nails, as always, the medical scenes and pandemic themes. Where M-fever was imagined just prior to COVID-19 and had symptoms in common; Riva Virus is the new threat and it mimics Monkeypox in that it is initially spread sexually. In Billy Raven’s world of 2088 it causes issues with fertility - or so he says.

It is also great fun whipping around the world with Billy and Indigo—from a Grammy Awards ceremony to Santorini circa 2005, to present-day Norway and to Mississippi 200 years before present time (at a time when the main way to put on women’s clothes was via dozens of tiny buttons). Though I missed having a date at the top of the chapter each time Indigo travelled.

I would recommend Indigo Moon to those who are hooked on the superhuman Black Spiral series. It is fascinating to see what the characters from that series are up to now. It also has some promising threads to follow—we haven’t seen the last of Billy Raven—and the new abilities the teens have discovered will be central to their future as they turn 18, join the BSI team and try and wipe out those who have nefarious plans for their genetic material.

Reviewed by Sarah Forster