Birt and Etho are best friends, they play on Sudden Hill, making
marvellous contraptions out of cardboard boxes. But then a new boy, Shu,
wants to join in too. Birt isn't sure that he wants Shu to join them.
Eaten up with jealousy, he goes home and refuses to come out to play.
Until Etho and Shu come to his house with the most marvellous cardboard
contraption so far.