Asterix: Asterix and the Vikings - Ren Goscinny

When the Vikings kidnap Justforkix, the timid but very trendy son of one of Chief Vitalstatistix' closest and most powerful friends, believing he has the key to the secret of the magic potion, Asterix and Obelix are sent on one of their most dangerous missions.
For they must voyage north to the Vikings' home territory and rescue Justforkix, before the Vikings find out he is not who they think he is, and make him pay the price.
Meanwhile, the fact that the Vikings' chief's daughter, Abba, has fallen for Justforkix only makes matters more complicated...