Percy is curious to know why there is a DANGER notice on the quay at Knapford Harbour. But, he soon learns not to trust trucks when he goes past the board and into the harbour!
- This book is based on the Railway Series story, Percy Takes the Plunge.
- This book was also sold as part of the Percy Takes the Plunge Wooden Railway set.
- There were two versions of this book published. One was green and the other was orange.