The Devil's Breath

There is poison in his heart. And now he wants to share it.
Nottingham, 1988. A family of four are found dead in their home, killed by a deadly toxin.
A few days later, an elderly couple are murdered. Also poisoned.
DCI Flint and his team are tasked with finding the killer. They quickly establish that the victims have a single, tenuous link - both families bought groceries from the same supermarket.
It’s the ultimate investigative nightmare – someone is poisoning food on a seemingly random basis. But why? Are they killing for pleasure? Or do they have some other motive?
Things become clearer when the supermarket receives a menacing letter demanding cash and threatening more murders. Flint realises he’s in a deadly race against time – if he doesn’t catch the killer quickly, more innocent people will die.
But how to even begin? The poisoner could be anyone and the poison anywhere.