The Dark Forest faces a challenge confronted by many sequels: when the hook of the first instalment was its central mystery, how do you keep readers' interest once that mystery is solved? (For an example of this dilemma see The Matrix sequels. Or better yet, don't.) In the case of The Three-Body Problem the initial central mystery boiled down to two questions: why are prominent scientists killing themselves and what does some weird virtual reality game have to do with it? By the end of the book it is revealed that it's all part of an extraterrestrial plot to invade Earth, and that humanity has only four hundred years before the alien fleet arrives. That gives The Dark Forest a great jumping-off point for its central plot, but how to keep the romance alive when the mystery is gone?

The answer: pose a new riddle. An obvious one is, "How will humanity survive the coming alien onslaught?" but even that's too easy. Cixin Liu throws a monkey wrench into the works by having the Trisolarans (the aliens in question) able to monitor everything that happens on Earth through the use of sophons, tiny particles that transmit everything they observe back to the Trisolarans (it also allows the Trisolarans to communicate with humanity when they wish to). The question then becomes not just how does humanity survive, but how do you outsmart an enemy that can see your every plan and listen in on every conversation?

One thing the Trisolarans can't do is read people's minds, so anything thought within the privacy of one's mind is still secret. A small comfort, but from this germ of an idea the UN enacts the Wallfacer program. In the program four carefully chosen individuals (a head of state, a scientist, a general, and our main protagonist, sociologist Luo Ji) are designated as "Wallfacers" and given the task of saving Earth. The idea is that the Wallfacers will independently come up with a plan to save humanity, each one enacting his own secret plan to deliver mankind from destruction. At their disposal are all the resources of Earth. They can request practically anything and never have to explain why they want it. No matter how erratic or asinine their requests might be, they must be honoured. If their actions seem pointless or puzzling, well, the whole point is to keep the Trisolarans from guessing what they are up to.

While The Three-Body Problem was mainly set in China, with a largely Chinese cast, in true sequel fashion The Dark Forest goes bigger, casting a wider net with prominent international settings and characters (for example, the four Wallfacers are Chinese, Venezuelan, American, and British). In Ken Liu’s translation of The Three-Body Problem it felt like there were a lot more footnotes on things relating to Chinese history and culture, while Joel Martinsen′s notes are usually drier comments on things like currency rates. This is also largely conjecture on my part, but it also felt like Ken Liu included more points of interest in the text itself. For example, there is a part early on in The Three-Body Problem where the book explains a character′s nickname, a little thing that would have been apparent already to Chinese readers. I′m willing to bet that line was Ken Liu stepping in to explain something for the book′s English audience. Martinsen's style of translation in comparison seems more plain and unembellished. This approach makes Martinsen as a translator less visible to the reader, and the scarcity of footnotes makes the book itself a smoother read (I am the type of reader who, when there is a footnote, needs to read it right away, giving me context but often taking me out of the story). Yet I still found myself missing Liu's notes. This difference between the two translators boils down to a common debate when it comes to translation: how much do you add/explain for readers not familiar with the culture? What considerations do you make when adapting a text for a different market? It can be a daunting challenge, since you can’t possibly hope to account for every culturally significant exchange, nor can you know how much any individual reader will be aware of it. Martinsen seemingly takes a step back from explaining things for a Western audience, though at no point did I feel confused about the plot or the characters. Style-wise Martinsen′s prose is to the point and clear, a good pairing when dealing with hard sci-fi like The Dark Forest.

Luo Ji is considered a puzzling Wallfacer choice by nearly everyone, including himself. When we first meet him Luo Ji is trying idly to remember the name of the woman he's been sleeping with for the past week. He's a washed-up academic, a young man already past his prime. When he's announced as the fourth Wallfacer, no one in the UN assembly is more surprised than him.

When Luo Ji tries to turn down the position he finds himself in a bind: everyone just assumes that his resignation is a fake, a front for whatever crafty Wallfacer scheme he's coming up with. After an attack on his life, Luo Ji decides to make the most of his unlimited power. Instead of using the resources at his disposal to come up with a plan for humanity, he decides to spend the rest of his days living in hedonistic bliss, scoring not only an idyllic mountain retreat but also getting his staff to hook him up with his dream girl.

And by that I mean his literal dream girl. Basically, Luo Ji has only ever been in love once, and that was with an imaginary girl he came up with. It all started years ago when his (real, flesh-and-blood) girlfriend challenged him to write a novel. Luo Ji imagined every detail of his heroine′s life, from her personality and physical appearance to her entire childhood and adult life. It′s not long before Luo Ji finds himself obsessed with his main character, preferring her company to that of real women. As Luo Ji explains to a doctor ″I′m madly in love with a fictional person from a novel of my own creation. I′ve been with her, I′ve travelled with her, and I′ve even broke up with my real-life girlfriend over her.″ (p. 92)

But now that he has the world on a string Luo Ji has the chance to actually find his dream girl′s real-life equivalent. He gives all the details of his imaginary girlfriend to his staff and asks them to track her down. The reasoning goes that with so many people in the world, someone just like the dream girl must exist. And she does, which is how sweet, innocent, almost nauseatingly pure Zhuang Yan is brought to live with Luo Ji at his mountain retreat. She′s a young, naive painter who one hundred per cent believes that living with Luo Ji will help him save the human race.

This plotline is one of my least favourite things about this novel. There are fascinating female characters in The Dark Forest: UN Secretary General Say, neuroscientist Keiko Yamasuki, spaceship captain Dongfang Yanxu. But Zhuang Yan never breaks free of being merely an extension of Luo Ji. She has next to no agency, and her greatest bit of character development is that she goes from being Luo Ji's dream girl to being a pawn used by the UN to finally spur Luo Ji into action.

While Luo Ji is lounging around in his mountain paradise, the rest of humanity is in turmoil. A big theme throughout the novel is that of hope versus defeatism. The victory school of thought says that everyone must be dedicated towards the goal of defeating the Trisolaran fleet, or else all is lost. The defeatists say that even with four hundred years to prepare humanity can't beat the Trisolarans.

According to the defeatists the smartest thing to do would be to load up everybody on spaceships and get the hell out of here. But that opens up a whole new can of worms: who gets to escape and who gets left on Earth to die?

Generation ships fleeing a doomed planet (and in a similar vein, giant underground bunkers built to help an elite few weather the apocalypse) have become a well-worn trope in Western science fiction, so that we take them for granted when they show up in genre stories. But The Dark Forest takes pains to point out not just how hard it would be to decide who out of all of humanity lives and dies, but also how the process itself would tear the human race apart. After flirting briefly with the idea of running away from the Trisolarans, the world instead decides to reject defeatism. Not only does it become illegal to build a "Noah′s Ark" ship, but defeatist thinking is scorned by the general public. Luo Ji compares the world′s all or nothing approach to an old Chinese novel called Floating City:

"Shanghai′s about to fall into the ocean, and a group of people go house to house seizing life preservers and then destroying them en masse, for the sole purpose of making sure that no one would live if everyone couldn′t. I remember in particular there was one little girl who took the group of one house and cried out, 'They still have one!'" (p. 56)

There will be no escaping Earth. Humanity will either defeat the Trisolarans or die together.

Of course, there is a drawback to focusing too much on victory: it's possible to overprepare and become too confident. About halfway through the book the timeline skips forward one hundred eighty-five years. Thanks to cryogenic technology, many key players from the main cast make the jump, including Luo Ji. When Luo Ji emerges from his cryogenic state he finds a world full of astounding technological marvels: they have mastered clean, unlimited energy and have a massive space fleet floating in orbit, ready to take on the Trisolarans. Luo Ji and his Wallfacer plans (whatever they may be) are not needed, he's told. Earth has everything under control.

Of course, this is not the case. When a simple probe arrives ahead of the Trisolaran Fleet, it makes quick work of the ships in orbit, destroying nearly all of Earth′s two thousand spaceships and showing humanity just how outclassed they are in this battle among the stars.

The devastation of Earth′s space fleet leads to one of my favourite parts of The Dark Forest. While most of the human space fleet was destroyed, five ships further out in space survived. These five ships band together and decide to start a new branch of humanity called "Starship Earth." Instead of returning to their home planet they set out in hope of finding a new habitable world. The moment when the five ships band together is a rare moment of triumph and hope, a bright spot in what is otherwise a dismal-looking landscape, a scene that makes you think that maybe everything will turn out all right after all. It's the equivalent of the scene in Game of Thrones where all the northern families declare Robb Stark King of the North.

But, well, look how well that turned out for Robb Stark. While "Starship Earth" gives humanity a glimmer of hope, it quickly becomes the darkest part of the book as one by one the captains realize just how slim the chances of finding a habitable planet are. And there's only so many supplies and too many people. Crewmates start falling into a deep existential depression. As one character puts it ″The Garden of Eden is growing dark. Blackness will swallow everything.″ (p. 448)

As in the original Eden, the danger is once again knowledge, in this case the knowledge each ship′s individual chances of survival would increase dramatically by attacking and cannibalizing parts and supplies from the other ships. While at first people are horrified at the idea, it soon becomes not a question of whether anyone is willing to cross that line, but who will do it first.

After the failure of Starship Earth it becomes apparent that, even if humanity wanted to, escaping into space isn't a viable option, and with the destruction of the fleet, fighting the Trisolrans doesn't seem to be on the table either. Luo Ji, as the only Wallfacer still active, is once again relevant as the only line of defence against the Trisolarans.

Luo Ji's solution circles back to the prologue, where he meets Ye Wenjie, a major character from The Three-Body Problem. While standing with him at her daughter′s graveside, Ye Wenjie explains the laws of the universe to Luo Ji:

"First: Survival is the primary need of civilization. Second: Civilization continuously grows and expands, but the total matter in the universe remains constant." (p. 13)

In other words, it′s the same problem faced by Starship Earth but on a galactic scale. Following through on Ye Wenjie′s laws leads to a revelation from Luo Ji:

"The universe is a dark forest. Every civilization is an armed hunter stalking through the trees . . . trying to tread without sound . . .The hunter has to be careful, because everywhere in the forest are stealthy hunters like him. If he finds other life—another hunter, an angel or a demon, a delicate infant . . . there′s only one thing he can do: open fire and eliminate them. In this forest hell is other people. An external threat that any life that exposes its own existence will be swiftly wiped out." (p. 484)

Luo Ji suggests that this explains Fermi′s paradox: the reason we haven′t discovered life on other planets is because they are keeping quiet for the sake of their own survival. Any civilization that loudly announces its own existence (like Earth has done) is just inviting other planets to either invade or destroy it outright.

And yet despite this bleak prognosis Luo Ji manages to find a non-violent solution to the problem with the Trisolarans, even reaching a tentative peace with them. Though the logistics of Luo Ji's plan are sound, after all the bleakness the hopeful tone of the ending feels slightly off. It's one thing for the Trisolarans and humanity to come to a shaky stalemate, but there's a sense of almost friendliness between the two species by the end of the book. At one point a Trisolaran (the one who tried to protect humanity in the first book) communicates with Luo Ji because it′s offended that Luo Ji said humanity was the only species capable of love.

"Perhaps seeds of love are present in other places in the universe. We ought to encourage them to sprout and grow." (p. 512)

After talking it over, both human and Trisolaran agree that even in a cutthroat universe, love is something worth taking risks for. Though it seems like an odd note to end on, I'm willing to give Cixin Liu the benefit of the doubt. By introducing the concept of the "dark forest" he has expanded the universe greatly, hinting at a much larger conflict than the one between the Trisolarans and humanity. I look forward to seeing how he caps off the trilogy in the final book, Death's End. He's already shown that he can write a satisfying sequel (one that, in my opinion, is even better than the first book) so now all that's left is to eagerly await the conclusion.

Shannon Fay is a freelance writer who has recently moved from Canada to the UK. She has also recently released a collection of short stories called Clever Bits. She can be found online at www.ayearonsaturn.com or @ShannonLFay.