Mr Benn has been invited to a fancy-dress party. He dislikes parties, but enjoys dressing up, so he looks round the shops for a costume to wear, but everywhere he finds only ordinary everyday clothes. Turning into a small lane on his way home, Mr Benn comes across a costume shop where he chooses an outfit of red knight's armour. Changing into the armour, Mr Benn passes through another door in the shop's changing room and finds himself in another world where he stumbles upon a dragon...
