While the Viking raids have come one after another for almost a century, in November 885, hundreds of Scandinavian boats sailing towards Burgundy present themselves before the walls of Paris and besiege the city. The stubborn resistance of Count Eudes makes it possible for the besieged city to resist until the arrival of Emperor Charles the Fat. In exchange for a large amount of money, he obtains the withdrawal of the Scandinavians. To protect themselves from the Viking threat, the king of the Franks, Charles the Simple, suggests a treaty to the Viking chief Rollo. This agreement is the beginning of the Duchy of Normandy. Part of the "Butterfly Effect" series.