It’s an arresting concept: the idea that rippling beneath the internet there is a dark twin breathing and growing. A place where drugs are sold; where hitmen advertise their services; where material to match any sexual urge can be found.

The Darkest Web is an exploration of this underworld known as the dark web, and Australian author Eileen Ormsby is your tour guide.

This is the second book from Ormsby, whose first, Silk Road, was an in-depth exploration of the dark web marketplace, based both on research and Ormsby’s personal experiences as part of the community. This new book takes a wider view of what else, aside from the sale of drugs, goes on down there.

What pulls you through The Darkest Web isn’t its often-nefarious, sometimes-gory details, but Ormsby’s handling of three progressively intense narrative arcs. Split into sections, the reader is introduced to a few key characters in the dark web world at each level: Dark is about the marketplaces that popped up after the owner of Silk Road was arrested in late 2013 (he was later jailed for life); Darker follows one man who is determined to have his wife killed but who doesn’t realise the hitman site he’s found is a scam; and Darkest takes the reader through the nightmarish world of “child porn” (which many people believe is the wrong terminology for child exploitation material) communities.

There are real deaths chronicled in this book, and Ormsby herself was at the receiving end of threats of violence for her reporting on the dark web on her blog, All Things Vice.

So what makes a London lawyer leave her job and make friends in such a place? “I was working in London in a Magic Circle firm for the one-percenters when the global financial crisis hit,” she tells Guardian Australia. “So that disillusioned me quite heavily and also got me interested in Bitcoin.”

Bitcoin is the most well-known cryptocurrency, the development of which was necessary for the proliferation of dark web marketplaces. Cryptocurrencies were “created to ensure that people had … their own currency” even if the big banks went down, she explains; Bitcoin also allows two people to transfer payments without knowing each other’s identities, making sales of drugs and other illegal items possible.

Most famous for selling drugs, the Silk Road marketplace was guided by an almost utopian philosophy. “Their idea was that people had a right to decide what they put into their own bodies and to buy those things if they wanted to, so long as they weren’t harming another person,” Ormbsy says. “But once Silk Road got taken down the markets that came after it were run by less scrupulous people, the people that were more likely to sell anything that could make them money.” Stolen identities and weapons, for starters.

The book might investigate a fake killers-for-hire site, Besa Mafia, but it does end with a real death, and Ormsby says it changed the stakes. Stephen Allwine, from Minnesota in the US, spent thousands of dollars and several months engaging the services of a hitman to kill his wife, Alice – and when no hitman came, he did it himself and tried to make it look like a suicide. Ormsby had been researching the site for a while, and had started trying to warn the authorities about people all over the world who were paying huge amounts of money to get people killed. “[Law enforcement agencies] were pretty much not interested. It was like, ‘Oh it’s a scam site, who cares’ and they wouldn’t tell us if they were following up on any of these things or not.”

Did the authorities simply underestimate the customer’s commitment to killing? Or was it simply that they didn’t know how to deal with it? “A bit of both,” Ormsby replies.

When Ormsby reported on Besa Mafia being a scam, she received threats, and at one stage was getting 20 or more emails a day. The owner of the site, known as Yura, was making hundreds of thousands of dollars and she was jeopardising his operation. “He really did think of himself as a Robin Hood of the dark web, going around scamming people out of the money they might have otherwise given to ‘real’ hitmen.”

Ormsby handles the third section – about child exploitation – with clarity and respect. Ultimately, too, it is hopeful. “It’s horrendous and depressing, but unlike the international taskforces taking down the drug networks – who are all disparate and who all want their own little piece – the international taskforces that are working on child pornography work together really, really well. And they’re working hard all the time. They are getting better and better at finding these people.”

Despite all the ugliness, Ormsby has found some not-so-dark places on the dark web to still take part in, including a community where “people gather and discuss things about the different dark web markets” and “a small psychedelics community” which is “like a little slice of sunshine and rainbows on the dark web,” she laughs. “It’s a really lovely little place with lots of happy people.”