Thanks to the nature of autism, many of us with the condition have other psychological problems that are either caused by our autism or overlap with it. Combine the rigid, obsessional thought processes associated with autism with the anxiety and poor coping mechanisms that are often part and parcel of living with the condition, and you have the recipe for obsessive compulsion. So it is, then, that at times of stress and anxiety we can slip into full-blown obsessive compulsive behaviour and lose all sense of proportion, driving the people around us to despair.

And when I say ‘we’, I mean my wife Lizzie.

And by ‘people around us’, I mean me.

And instead of ‘being driven to despair’, a better metaphor would be that I am steaming uncontrollably towards a mid-Atlantic collision with an iceberg on a dark April evening. All because of half a freaking banana.

It all started a month ago when we returned from holiday. Every night after I’ve put Izzie to bed, Lizzie goes around the lounge and tidies up the baby’s toys. And given that Lizzie’s other big obsession right now is buying toys for the baby, we have an awful lot of them. Before going to Toys R Us to get something, I just check the massive pile of plastic bags stacked up in the corner of the study, and odds are we’ll already have at least two of what I’m considering buying.

Anyway, Lizzie’s particular inclination is that all the toys have to go back complete – if the toy food blender has six shapes that go inside it, then when it goes back on the toy shelf it needs to have six shapes inside it. Not five inside it and one in the box of building blocks, but all six inside it. This is non-negotiable and woe betide anybody who forgets.

So, a month ago we return from holiday, play with Izzie for a couple of hours, and then I put her to bed as usual. Lizzie tidies the lounge and – gasp – half the toy banana from the kitchen set is missing. We have both halves of the tomato, the pepper and the carrot, and the three parts of the cucumber, but only one half of the banana.

In the normal scheme of things, you might think this is minor. I thought so myself, it being a two-inch long piece of yellow plastic with a bit of Velcro stuck to it. Unfortunately, I hadn’t realised that in Lizzie’s mind it was the Holy Grail and it had just been stolen from us by person or persons unknown.

My reassurance that ‘it’ll turn up eventually’ didn’t cut the mustard. Before the holiday, the sacred banana had been complete, entire, unsullied – Izzie had only been in the lounge a couple of hours upon our return, thus it could not have gone very far. We had to find it.

Many hours after midnight, having overturned the sofas, emptied all the drawers and cupboards, removed the building blocks piece by piece from their boxes, turfed the dog out of her bed, checked behind the fridge, in the cat litter and around the driveway (as if!), I managed to persuade an increasingly irascible Lizzie to come to bed, we’d find it later. Problem solved – or so I thought.

The following day we repeated the exact same process, double and triple checking all the places we’d already double and triple checked the night before. I ended up checking through the bins, the nappy bin, the freezer, inside the guitars, stretching my hands into deep, dark crevices no mortal ever dared to delve. Still no banana.

Long after midnight, I managed to persuade Lizzie to come to bed, where she tossed and turned all night, no doubt dreaming of incompleteness.

It was two-thirds of the way through the third day of the search, after putting the baby to bed and moving the sofas for perhaps the eighth time, that I finally declared enough to be enough. Actually, I think what I might have said was something along the lines of, ‘I’m all out of f**ks to give about half a goddamned plastic banana! Don’t ever mention it to me again, I don’t care anymore, there’re another two plastic bananas in the corner of the study anyway, for God’s sake, let me live, why won’t you let me live!’ And suchlike and so forth.

Two days later, Lizzie stopped moving the furniture. Two days after that, she stopped talking about the banana.

But the stage was set. The anxiety was there. And it manifested itself late every evening with the words, ‘Have you seen…?’

Every evening for the past month, Lizzie has lost something and pressganged me into helping her find it. Mostly it’s Izzie’s hairclips, less than an inch long, or her dummies, transparent. Sometimes it’s pieces of paper, a scrap torn off the back of an envelope on which she has written the world’s most important information. Quite often it’s socks, which necessitate going through the sleeves of every item of clothing we own in case it’s become lodged inside in the wash. Occasionally it’s earrings, tiny, insignificant, nigh-invisible earrings. Every single evening, give or take.

I’ve been under the sofa so many times now, I can describe it better than the back of my hand. The inside of the dustbin no longer holds any mysteries. The sound of building blocks being removed from the box one at a time fills me with dread, and every time I hear the words, ‘Have you seen…?’ my blood chills within me. No, I haven’t seen it. But I guarantee we’re spending the next two hours searching for it.

There are two possibllities for explaining this behaviour. The first is that, because both sets of our parents were away, Lizzie has been anxious for the last month, and this anxiety has triggered an obsessive need to have control over the minutiae of our household to distract her from her own feelings of vulnerability. Once triggered by the missing banana, her mind became stuck in a loop of repetitive, obsessive behaviour, fostered by her rigid autistic way of thinking.

The second is that she’s faking all these disappearances and we’re still searching for that flipping plastic banana!

Which does, to be fair, remain something of a mystery…