Biggles and the team help unravel a smuggling operation being run from a small island off the north coast of Scotland.

Dispatched to the island to help the new owner, Macaster, explain the occasional aircraft visit, the team really do end up 'roughing it', moving from boat to ruined cottage to cave in short order. The bad guys are esconced in the castle and Biggles plays it softly softly trying to work out what they are up to. However even he gets bored of that eventually and so its time for a showdown.

Following a few dead-ends and obligatory splitting up of the party, turns out the bad guys are making whisky on the island to supply one of the gangs nightclubs in London. The operation is staffed by ex-crims lying low after surprise exists from the prison system.