It is this boy's hyperactivity that dominates the family - and indeed the whole of this gripping new drama. In the title sequence for the first episode, the parents, Alex (Douglas Henshall) and Theresa (Clare Holman), are desperately trying to restrain the rampaging Danny (a stunning debut from Eric Byrne) in a supermarket.
As Danny runs amok - eating lollies he hasn't paid for and tipping basket- loads of sweets onto the floor - Alex takes out his exasperation on his wife: "What do you want me to do? Tie him to the bloody trolley?" When a horrified bystander then asks Alex "Can't you control him?" he replies with a blunt "No!"
Theresa, too, is nearing the end of her tether over Danny. "It's relentless," she sighs to Alex. "We go from one shitty moment to the next, without anything in between. When do I get to love him?" Later in the episode, Alex's frustrations with his son spill over into shocking violence.
Although his parents don't yet know it, Danny has ADHD (Attention Deficit and Hyperactivity Disorder), which causes problems with concentration and discipline. The series is being billed as "semi-autobiographical": Marchant has a teenage son with Asperger's Syndrome, a mild form of autism, and has used his own experiences to help with the background to Kid in the Corner. Marchant also drew on stories from parents of children with ADHD, attending several conferences on the subject.
"Your biggest responsibility as a dramatist is to tell the truth," he says. "Whatever happens in this drama has happened to real-life parents of children with ADHD. No doubt there will be criticism of Kid in the Corner, but it will be misplaced because I've only told the truth."
Marchant insists this is not merely a drama about dealing with special needs. Uncom-promising yet deeply moving, it will certainly raise awareness about a much-misunderstood condition. But the series shouldn't be limited to an examination of one particular children's disorder; it is meant to be a more general reflection of the growing stresses that all parents are under.
Marchant says: "This is a story that every parent - and every teacher - will recognise. Some people may never have had to make the choices that parents of children with special needs have to make, but everyone understands difficult children. I wanted to show that it's not always easy to love our children, but ultimately what's most important is showing them the love we do feel."
Kate Anthony, the producer, agrees. "Any parent who watches this will say, `I've come very close to snapping like that'. It's typical of family life in general. It's about two parents who are constantly knackered, people who are stretched in too many directions and trying to hold on to their own relationship at the same time. That will be familiar to everybody."
Bille Eltringham, the director, hopes the drama will have universal resonance for stressed-out parents (is there any other kind?). "All parents are in a really difficult place now," she says. "With school league tables, there's more pressure on them. Above all else, people feel able to advise you about being a parent - `You should be doing this or that'. In this drama, ADHD is neither here nor there - it's just a vessel to talk about general anxiety. There's a low-level feeling that there's a malaise, that something's wrong and that something must be done about it. Kid in the Corner is about the responsibilities heaped on parents these days. Everyone is obsessed with finding out why their child is not perfect."
Kid in the Corner starts Wednesday, 9pm, C4