Bedtime stories! One of the nicest slices of a parent’s day: your child all cuddly and sleepy and pyjama-clad, the book propped cosily between you so that you can pore over the pictures together. Plus – let’s not beat about the bush – that joyful anticipation of liberation, the knowledge that you’re almost off-duty for the evening and there’s a bottle of wine with your name on it waiting in the fridge, to be opened just as soon as the lights go out. But along with all that, bedtime stories can lead to some strange questions, too; questions that steer you into unexpected conversations.

‘Why is the stepmother always bad?’ asked Fergus last night. We’ve borrowed a book of fairy-tales from the library and have been reading them a lot recently. And he’s right – the stepmother of fairy-tales is always frightening or murderous or vengeful. Beware the stepmother with her poisoned apple and magic mirror! Mind she doesn’t send you off with a woodcutter, instructed to put you to a violent death in the depths of the dark forest!

‘That’s a very good question,’ I replied – which, as you may know yourself, is every parent’s quick-let-me-think-up-a-decent-answer response. And then I was stuck. Because . . . well, not to put too fine a point on it, sometimes in real life the stepmothers are actually the heroes who come riding to the rescue and make everything better, aren’t they? If you ask me, it’s the actual mothers you’ve got to watch out for.

Before you start getting het up and thinking: Excuse me, I’m an actual mother and I’m certainly not murderous or frightening, thank you very much – I’m really only thinking of one person here. Fergus’s biological mother, in fact. Yes, readers, she’s back. With a thunderclap and some horror-movie music, and possibly a magic mirror of her own, she has returned to our lives. A happy reunion? Not exactly. Turns out that, just like all the most evil fairy-tale villains, she’s hell-bent on shaking things up for the worse.

‘So what do you think?’ Craig asked impatiently.

Sitting in front of his laptop screen, Frankie blinked. She’d only read halfway down the page so far and wasn’t sure she wanted to continue, guessing that there was worse to come. ‘This is a joke, right?’ she asked weakly. It had to be a joke, she thought, seeking confirmation in his face. Craig’s columns were usually warm and funny observations about family life, the sort that left you feeling uplifted. Vindictive and spiteful attacks had never been a feature of his writing before.

He seemed surprised at the question, though. ‘Er . . . no,’ he replied. ‘It’s not a joke.’