My wife and I are watching TV, but there is a loud and persistent scrabbling sound coming from under the sofa, travelling from one end to the other and back.

“Can you turn it up?” I say. My wife points the remote at the screen. Something small and grey with a long tail shoots out from beneath the sofa and streaks across the room, pausing briefly to gnaw at the corner of the rug before disappearing under a desk.

“Explain,” I say, “how this is different from having a rodent problem.”

“It’s a kitten,” my wife says.

“It’s the size of a rat,” I say. “And it does mostly rat things.”

“I’m trying to watch this,” she says. At that moment I feel a series of tiny needles penetrating the skin of my leg through my trousers. I clench my teeth as the needles travel up my shin, until a little face is peering at me over my knee.

“Can I help you?” I say.

In the 15 years since we last had a kitten, I’d forgotten how much worry is involved: you have to take constant care to avoid stepping on it, and you have to check that it’s not in the dishwasher before you turn it on. You spend half your day looking under things for it, and the other half patiently letting it unknit your jumper from the sleeves inwards, because at least you know where it is. It’s asleep whenever you want to play with it, then it stands on your plate while you’re eating.

At first I spent a lot of time trying to exhaust the cat by playing with it, but it never gets tired of anything. My wife bought a little plastic fishing rod with a length of string and a small stuffed fish at the other end. Using this to entertain the cat is actually a bit like fishing, but unlike a sea bass, the cat is always biting. Eventually, I learned to prop up the rod between two sofa cushions so I could read.

The kitten came knowing how to use a litter box, which is a plus, although the thing it does immediately afterwards – deftly flicking the turd into the middle of the room, like a golfer hitting out of a sand trap – I don’t know where it learned that.

“When you’re no longer cute,” I tell it, “none of this will be tolerated.” In the meantime, however, it seems to understand that everything it does is potentially Instagrammable.

One morning, about a week after its arrival, I come downstairs to find the kitten riding the tortoise around the kitchen. I like to think I’m a good judge of unhappiness in a tortoise, and I was seeing all the signs: the downcast eye, the craning neck, the blooming lake of piss in his wake.

“You can’t do this,” I say to the cat. “You’re distressing him.” The cat gives me a look that says: did you get a picture yet?

“Fine,” I say, taking out my phone.

Even the tortoise is not as unhappy as the dog, which is simultaneously perplexed and terrified by its tiny new enemy. The dog and the old cat reached an uneasy detente over many years, apart from the occasional stand-off either side of the cat flap. Now the dog is being stalked for a minimum of six hours every day, even as it sleeps. Its patience seems bottomless, but its nerves are beginning to fray.

I am also being stalked: as I step into the kitchen, the kitten leaps out at me from behind a bin, before changing its mind in midair and withdrawing again as if pulled by elastic cords.

“When can it live outside?” I say to my wife.

“In two weeks,” she says, scooping up the kitten from its hiding place.

“It’s already been two weeks,” I say.

“He needs to be chipped first,” she says. “And he needs his second lot of injections. Hold this.”

She hands me one end of a large plastic syringe, wedging the tip of it between the kitten’s jaws.

“OK, squeeze,” she says. The kitten does not like this at all.

“What was that?” I say.

“De-worming paste,” my wife says.

“When did it get worms?” I say.

“They all have worms,” she says.

“They all have worms?” I say.

“They’re born with worms,” she says, releasing the cat.

“I can’t believe what I’m hearing,” I say. “This cat walks across my lunch every day.”

“He’s not supposed to be on the table,” my wife says.

The cat has positioned itself behind a table leg, where it sits and looks up at me with big round kitten eyes.

“Worms,” I say. “Nothing Instagrammable about that.”