The Flying Doctors (1986) : 7x5

David and Annie go to a remote part of town to do check ups on pupils at the school. One of the boys keeps acting strangly and has bad headaches and his hands keep shaking, his sister is having headaches aswell. The other kids tease him and think he is mad. David tries talking to his father but gets no joy from him, so he goes to see the boy's grandfather. He has got the shakes aswell and says it's miners shake, David finds out from him that stuff from the mines has been leaking into a stream, but then they find out it is getting into water where the boy's father is getting water from to water the vegetables with, so it turns out the boy is being poisoned.