Archie is off on another adventure! This time, after his exploits on the London Underground, he has a mystery to solve on the fascinating island of Iceland.

When Archie's Dad, a lecturer in Medieval History at the local university, has to visit Iceland for a weekend to research the remote island of Viðey, two kilometres from the mainland, he decides to take Archie with him.

They are met on Viðey by the renowned and fierce Icelandic archaeologist Professor Margret Magnusdottir, their host for the weekend, and Reverend Gudjonson, minister of Viðey Church.

From Reverend Gudjonson, Arhice and his Dad learn that a foreign businessman, Hank Trumpslick, is trying to turn the beautiful and historical Viðey House and Church into a hotel for his own financial gain.

Learning more about the island of Viðey, Archie and his Dad realise the wonderful history and ancient stories belonging to the island and decide to help Reverend Gudjonson in his fight against Hank Trumpslick and his greedy plans for the hotel.

But what are Professor Magnusdottir's real motives? As Archie and his Dad find themselves locked in the ancient Church of Viðey, they realise Professor Magnusdottir has equally selfish plans. With the help of a mysterious island spirit - one of the the so-called 'hidden people' - Archie must stop Trumpslick before it's too late...