L`isola di ghiaccio e di fuoco

Martin mystere and Sergej Orloff are together once more, but this time as allies, heading towards Iceland "The island of ice and of fire". They are on the tracks of Saint Brendan, the Irish sailor monk; their guide is a mysterious Runi shield, left in America a thousand years before by the Vikings. During their investigation, the two former enemies once again follow the path of Siegfried, the legendary killer of the dragon of the Nordic myths...

While researching about vikings that came to America before Columbo, Martin finds old picture of Chico & Guthrum. Guthrum is Viking king that we saw in couple of Zagor episodes (Zagor 63).