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.
Rosie is incredibly excited - Gandalf is finally coming because there is 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.
Rosie becomes obsessional about Christmas, unable to understand why it can’t be Christmas all the time. In 2007, Si and Em continue to drift apart and consider splitting up.
As Em gets excited about Si’s annual quiz, Rosie becomes fixated on making her draw a specific picture over and over again. In 2008, Rosie suffers a frightening medical emergency.
After the school notices some bruising on Rosie, Si becomes paranoid about a visit from social services. In 2008 Rosie takes her first steps leading to unforeseen new problems.
Rosie's excited as they set off for the annual summer holiday but things are not as she was expecting. In 2009 Si and Em are confronted with Fliss, their perfect new niece.
The family struggles as Rosie hits puberty. She becomes erratic before, out of the blue, her genetic condition is diagnosed, and Si and Em come to terms with why Rosie is Rosie.