The story is set in the final days of WWII; Selina, who has been living with her cousins for the duration (her parents are prisoners of war in Hong Kong), is sent a beautiful party dress and shoes by her American godmother. But with shortages of fuel and food, there are no parties or dances where she could wear it. Everyone agrees that it would be a tragedy if she doesn't get the opportunity to wear this fabulous frock at least once, and the large and energetic family of cousins come up with a solution: they'll put on an historical pageant at the nearby manor house (as you do), which Selina can introduce, dressed up in The Frock.
Events rapidly get out of hand, with Philip, the theatrical nephew of the manor house family taking over as producer (he's also a wounded Squadron Leader, so there are no niggling worries about his manliness...) Before the cousins know it, the pageant has swelled to include everyone in the village -- hordes of dancing children, forty-two knights on horseback, a hundred monks dressed in blackout material, American soldiers in jeeps sweeping across the lawns.
It's not until the dress rehearsal that Selina steps forward to give her prepared prologue, dressed in her precious frock. And then Philip dismisses her. 'Get off the stage, ducky, you're holding up the first scene.' He hasn't even realised that the whole point of the pageant was an excuse for her to wear her beautiful party dress.
Noel Streatfeild is always strong at juggling various strong characters with clashing agendas, and she is wonderful at the detail of theatre, dance and performance. The chapter devoted to the various provisions of all the hundreds of costumes that need to be supplied is simply riveting. I did squirm slightly at the classist story -- the cousins are all very comfortable ordering about the villagers and the manor house servants, who meekly submit. Even the nine year old is allowed to get away with speaking to her elders in a really bossy and disrespectful way. Also crying is really, really shameful, even if you're only eleven and your parents are prisoners of war.
But I can forgive. Party Frock has earned its place on our Girls' Book Shelf of Pride.