A distress call from a satellite phone comes in from the uninhabitable granite islet Rockall. The casualty was out raising money for charity when the weather turned for the worse and became a threat to his life. Approximately 240 nautical miles away in Stornoway, Coastguard Rescue Helicopter 948 is the only option with the capability to help save the casualty, even though the tasking is just outside their operational remit. So time and fuel are the key factors to everyone's survival.