Inside the vivarium – a secure glass climate-controlled tank – was a dark grey cobra lying in a curl of mottled coils. At the sight of her, he began to unwind, lifting his stubby snout, his forked tongue flickering out inquisitively. As always, she was entranced. She loved the way her snakes moved – so smooth and sinuous. She loved their shiny black eyes – like dark gemstones. She loved the geometric tessellations of their scales. And, more than anything, she was enraptured by their lightning-fast deadliness. They were her babies, and on occasion they were also her executioners.

She reached up, lifted the top of the vivarium, and dropped the mouse inside. It landed on the floor of the tank, standing there for a second, motionless, its whiskers twitching. In the same moment, the cobra whipped its head around to pounce on it, sinking its long fangs into the white fur, injecting the mouse full of deadly venom. The mouse didn’t even have time to squeak. The cobra gulped its lifeless body down in a single mouthful.

She smiled and moved onto the next vivarium. The room was full of such glass tanks, all of them containing cobras of different species, from all over the world – from Africa, India, South-East Asia. She kept them all here in this particular residence – an old-fashioned high-ceilinged apartment situated in a red-brick mansion block in West Kensington.

The apartment block had been designed to attract the wealthier classes back in the nineteenth century when it had first been built, and it was still populated by those types of people today, the kind of people who kept themselves to themselves, the kind of neighbours who suited someone like her just fine.

The apartment was just one of a number of properties that she owned in London and elsewhere. As an ostensibly law-abiding citizen, this flat was where she mostly resided for the purposes of appearing normal. And looking normal was crucial when it came to conducting business successfully.

If the neighbours ever did speculate about her, they probably thought she was just some well-off, stylishly dressed young woman with a taste for fedora hats who dabbled in the fashion industry or the art world and who happened to be blessed with rich parents who were willing to subsidise her lifestyle and pay for her flat.

And as for the name they knew her by, it was just one of many assumed names that she’d used over the years. A nice normal forgettable name. Like a nom de plume. But, of course, Mister Snigiss was who she really was…

Standing in front of the next vivarium, she leaned in so that her face was just a few centimetres away from the snake on the other side of the glass. His name was Sidney and, out of them all, he was probably her favourite – an Egyptian cobra, copper in colour with a brown mottling down his spine – a magnificent creature, almost two metres long. He began to stir, rearing up, spreading his hood and emitting a long sibilant hiss.