By Philip Hewitt
Published: September 16, 2013.
Anna and Matthew from Stevenage are spending their Easter holidays with their uncle and cousins in the Usk valley of south-east Wales. Their Uncle Richard, is a Countryside Warden and suspects that someone is tipping industrial waste sludge into local waterways. When Anna is woken late at night by the sound of a heavy truck driving up the hill past Canal House, she becomes suspicious. Read on!