Sam says the word "Thursday" one too many times next to the magic book and lands himself, Joe, and Fred in 1000 A.D. Vinland, narrowly escaping a Viking blitz and setting off on a voyage to Greenland with Leif Eriksson.
Fred, Sam, and Joe get a chance to sail with Leif Eriksson when they accidentally transport themselves to Canada, circa 1000 A.D., at the time of the Vikings' arrival in North America.
