The subject of this story is a campaign to save the local pier in which Tim Traynor (the toothless wonder) and his teacher recruit the son of the local development firm as a double agent. Other books by the author include "The Toothless Wonder in the Tower" and "A Gift from Another Galaxy".
Used availability for Philip Curtis's The Toothless Wonder and the Double Agent
Hardback Editions
October 1988 : UK Hardback