Rosie Yates is a nine-year-old girl with a severe learning disability due to an undiagnosed chromosomal disorder, living with her dad Simon, mum Emily and brother Ben. It's a typical Saturday for the family, starting with an attempt to get Rosie to the park for some fresh air. She refuses to cooperate, and afterwards she's similarly uncooperative with her dinner. As Simon and Emily are later distracted, Rosie causes carnage in the kitchen.

It's bath night for Rosie and, as usual, that means chaos as she insists on having all the bubble bath. Emily decides that she needs to form a strategy, she lays a trap for Rosie, putting the bubble bath out of reach, then leaves the bathroom and waits. Rosie falls for it, and Emily wins this round of `bubble chess', but the game becomes more complex as Rosie twigs what is going on.

A trip to Rosie's favourite place, the swimming pool, ends in disaster when she decides she hates it. Emily begins to wonder if it's just that Rosie wanted to do something else more and becomes fixated on working out what Rosie wants. Simon goes off to take pictures of all the places they regularly visit to put together a booklet. It raises some eyebrows when he has to explain to parents why he's photographing playgrounds and paddling pools, without an actual child with him.

Simon's mum and step dad, Grandad John, a bluff no-nonsense Yorkshireman, have come to stay. They're never shy of offering up their opinion on Simon and Emily's less than perfect parenting skills.They explain that their plan is to take Ben back down to Devon for three weeks in the summer which causes Simon and Emily to wonder why aren't they willing to take Rosie?

Rosie is incredibly excited, Gandalf is finally coming because there's going to be a birthday with lots of presents. It doesn't matter to Rosie that it's Ben's birthday. The extended family set off for a birthday meal, via Pizza Express because Rosie insists, although when they get there she, as usual, refuses to go in because it's too loud.

Rosie starts to say the word `mama', raising hopes that her communication will finally take off. Feeling totally outshone by Rosie's amazing school teacher Abigail, Em concentrates on trying to develop Rosie's sign language.