In Adam-Troy Castro's novels, Andrea Cort was born on a colony world where humans and the native aliens lived in total harmony – until one day, everyone in their community went mad and killed each other. The only survivor, Cort was eight years old, but she was still branded a war criminal, which makes it harder for the grown-up Cort to travel around investigating murders in extreme environments in space.

Part of the fun of these novels seems to be where Castro will put Cort next: the first book, Emissaries From The Dead, takes place in a weird tube-shaped habitat where some humans live in the upper branches, at constant risk of falling hundreds of miles into toxic atmosphere. The second, The Third Claw Of God, takes place on a space elevator, which stalls out just outside a planet's atmosphere. People are constantly accusing Cort of being a monster, and she half believes it herself.

Cort's a counselor with the human Diplomatic Corps, but in the first novel she becomes a secret agent of the godlike artificial intelligences that run the universe, the AISource. The AIsource is searching for a way to die, a plan which a splinter group of AIs opposes bitterly, and Cort has promised to help the AIs die because she hates them and blames them for her problems.

Meanwhile, Andrea Cort has one of the most fascinating romantic relationships in science fiction. In the first novel, Emissaries From The Dead, she met the Porrinyards, a man and a woman whose consciousnesses were linked cybernetically, making them one person with two bodies. The Porrinyards and Andrea fell in love, and in the second novel, they're a couple – or a threesome, depending on how you look at it. The Porrinyards may have a single mind, but they're also capable of being in two places at once, and concentrating on different things at the same time. Oh, and it doesn't hurt that both their bodies are shockingly attractive. In one of the novel's hottest scenes, the Porrinyards wake from cryo-sleep extremely horny – apparently it's one of the main side effects of interstellar travel – and they have a hot threeway with Andrea in the shower. She loses track of which one of her hot lovers is doing what to her, after a while – but it doesn't matter anyway, since they're only one person.

I think that's the main reason I enjoyed the second Cort novel, The Third Claw Of God, even more than the first. Castro spent a lot of time setting up Cort's situation in the first novel, and now that it's in place, he can have a lot more fun with it. We get to see how, in practice, a relationship with a linked pair would work out – especially as the Porrinyards help Andrea investigate a particularly sticky murder. The Porrinyards want Andrea to join them and become a third linked mind in their gestalt entity, but they're content, for now, to love her as a separate entity. And they're a huge help to anyone investigating a murder, because they can be in different rooms and still know everything the other knows. They're the perfect Watson to Cort's Holmes. Unfortunately, one of Andrea's main modes of thought is rage and paranoia, so she's constantly accusing her lover(s) of hiding something from her. And we also see how complicated her life as an agent of the AISource is really going to be.

I already loved the first book, Emissaries From The Dead, for its crazy setting, the weird interactions with AIs and our first meeting with the Porrinyards. But the second book has fully sucked me in – for one thing, it's clear this isn't just going to be one of those series where Cort goes around having stand-alone adventures and investigating locked-room murders in weird space stations or whatnot. The second book moves forward the story of Cort's life as an AI secret agent in a meaningful way, and also gives us a totally new spin on Cort's situation. It's not quite that everything we thought we knew was wrong, more like we're seeing it all from a totally new perspective as we learn a bunch of new facts.

So what's the murder mystery this time around? As I mentioned, it takes place on a space elevator on its way down to the planet Xana, which is owned and operated by the evil Bettelhine family, a clan of weapon-makers, whose influence goes back centuries. They've invited Cort to their planet to talk about a business proposition, of sorts, but before she even makes it down to the planet, murder strikes. An elderly scholar, who just happens to be from the planet where Cort was branded as a war criminal, gets murdered with a 15,000 year old weapon, the Claw Of God, which liquefies you from the inside out.

For a good chunk of the novel, the space elevator turns into the Orient Express, with Cort interviewing suspect after suspect inside its luxurious but limited confines. And in the tradition of all murder mysteries, she uncovers a lot of facts that appear unrelated to the case, but which prove that the Bettelines are even worse than she'd realized. Bad enough that they are responsible for wiping out tons of civilizations in their drive to provide newer and deadlier weapons to all contenders. But it turns out there are actually worse things than weapons of mass destruction, and the Bettelhines are up to their necks in all of it. And then we learn that the Bettelhines have more of a tie to Cort's past, and to her possible future as the slayer of the godlike AIs, than we'd realized.

As with the first novel, The Third Claw Of God becomes much less about "whodunnit" and more about other issues, so that by the time you find out who the murderer is, you're already caught up in larger issues. (And the identity of the murderer might be a slight letdown, but only if you're not already fascinated by the bigger picture of AI civil war, criminal families with deadly secrets, and weird weapons that can do more than kill you — they can enslave you.)

In the end, Andrea Cort has to ask new questions about who she is as a person, as well as where she comes from and what she stands for. And her answers to those questions may end up helping to shape the future of the human race, although — as the AIs wryly tell her — that doesn't mean she should get an inflated sense of her own importance. She's stilll just a pawn, only in this case she's a pawn that's in a crucial spot.

I feel like I should rave more about these books, because they haven't been getting as much buzz as they deserve and I love them. The Andrea Cort novels are almost a guilty pleasure, except that in between all of the great derring do, detection and romance with the psychically linked pair, Castro manages to ask some really interesting questions about the nature of humanity and how far you'd be willing to go to stop the galaxy from being filled with lethal weapons. These books are compulsively readable space mysteries, but they're also hiding little packets of cleverness and substance under the surface. Highly recommended.

In Emissaries From The Dead, Andrea Cort is an investigator for the DipCorps, the humans' diplomatic organization which keeps its members in a form of indentured semi-slavery in exchange for getting them off their hellish homeworlds. Cort has her own horrendous secret, and has been branded a war criminal, but corruption turns out to be the norm in the DipCorps. (One feature I liked about Emissaries was its use of spaceships with sleep chambers in place of the easier magic faster-than-light drive. It means Cort is really on her own in dealing with the unknown murderer.)

Cort gets assigned to One One One, a tube-shaped artificial environment completely with artificially engineered intelligent life forms, the Brachiators. The habitat has artificial gravity, artificial suns... and a horrendous toxic atmosphere at its center. The humans live in a maze of hammocks hanging over a sheer drop into the toxic cloud. Oh, and did I mention the A.I.s have created anatomically correct dragons, which fly around just below the humans' levels, breathing fire at anyone who comes too close?

I don't want to give away too much of Emissaries' plot, because the twists and turns are a huge part of its appeal. I will mention that it reminded me of a Ross MacDonald novel, in that Cort basically stomps into this complex nest of relationships and secrets, and leaves them a shambles. Pretty much everybody has a secret, and she can't solve the main mystery until she uncovers the corruption and internecine warfare that have been going on long before her arrival. The actual murder mystery involves two women who have been killed in spectacular and gruesome ways, by someone who keeps sending Andrea Cort bloody and disturbing holograms of her own torture and murder. (To be fair, though, I sort of guessed the central murder mystery about a third of the way into the book, but the world-building and other mysteries were absorbing enough that I didn't care that I was right.) Andrea Cort is almost comically reckless, with a death wish mixed with a willingness to do whatever it takes to force her opponent's hand.

The other awesome aspect of Emissaries is the Porrinyards, a male-female couple who are cy-linked, meaning they've become one individual with a shared consciousness. They often speak in unison, and have sex with other people as one person, so it's sort of like a threesome but sort of not. The gestalt-duo thingy means that they can be apart, but each of them knows what the other is seeing. (And when only one of them is asleep, he/she can shape the other's dreams.)

The way the novel ends, plus the "An Andrea Cort Novel" tag on the front, makes it look as though this is the first book in a series of standalone mysteries set in this universe of enslaved diplomats and semi-omnipotent A.I.s. I really hope that turns out to be the case, because both Cort and her universe have terrific scope for development. Emissaries From The Dead [Amazon.com]