Heartbeat S12E14 - Out of the Blue

Vernon and David are involved in a serious car accident whilst driving a tanker filled with a mysterious substance, which pollutes the local reservoir and leaves everyone in Aidensfield struck down with a mysterious bug. Luckily, the staff of nearby St Aidan Royal Free hospital are on hand to offer assistance, but with Vernon apparently suffering with bouts of amnesia, tension boils over as the local authorities remain unaware of the truth behind the threat, and things escalate when David receives a threatening phonecall than puts both his and Vernon's lives in danger.