In 943, a pagan king called Setric arrived with a fleet on the Seine, seeking to ‘take over the whole area without a grant from the king’ and to bring the young Richard and his Rouen Northmen back ‘to the worship of idols, and to bring back pagan rites’. But this was not to be because the young Carolingian king Louis IV d’Outremer was quickly on the scene and engaged Setric and his dux Turmod in battle. Louis’s mounted forces were victorious and both Setric and Turmod were killed. As the great French historian Philippe Lauer said: ‘La défaite du viking Setric et du renégat Turmod est un événement important dans l’histoire de l’établissement des Normands en Neustrie’. The mystery examined in this article is, who was this pagan king Setric (ON Sigtryggr) who had been sent to Valhalla? And where had he come from —York or Denmark? It is shown that whilst a Danish origin for King Setric cannot be completely excluded, the equation of a King Sihtric of York with King Setric on the Seine is more likely and is supported by a plethora of onomastic, chronological, numismatic and contextual evidence.