He had done it! Jack had finally done it, he defeated Aku!
As he struck the final blow Aku cursed Jack's name. Aku melted into a shapeless liquid form, and Jack collected him in an enchanted glass phial given to him by a tribe of monks so that he could perform a ritual to completly destroy later Aku's essence after returning home. Jack leaped through the portal to return to his own time... or so he thought.

To his surprise Jack had arrived in a much different time and space than either he had previously been, ours.