After Mr. Whittaker visited his ancestor Albert in medieval England, valuable treasures began to disappear from Lord Darkthorn's collection. If the treasures weren't returned, Albert would be punished and locked in a tower. The Imagination Station wouldn't work for Mr. Whittaker, because he left a family ring in the past, and the machine thought he was still there.
Since Mr. Whittaker couldn't go himself, cousins Patrick and Beth went on missions to retrieve the treasures and save Albert. Their fourth trip took them to England where they discovered the real thief and cleared Albert's name. Before Hugh, the thief, could be caught and punished, he stole Mr. Whittaker's ring, which allowed him to travel through time. Beth and Patrick followed him to keep him from changing history. On their last trip, they were able to retrieve the ring from Hugh but not before he jumped through time once again.
After Patrick and Beth return to Whit's End, Mr. Whittaker is able to trace Hugh to Plymouth in 1621. Even though the ring has been returned, the Imagination Station still believes that Hugh is Mr. Whittaker and won't allow Mr. Whittaker to travel back in time.
Mr. Whittaker asks Beth and Patrick to help him one last time by returning Hugh to medieval England and Lord Darkthorn's castle. The cousins agree, so Mr. Whittaker gives them the proper clothing and a few gifts. He gives Beth a beautiful golden mirror and Patrick a mysterious leather pouch. Mr. Whittaker tells them if they grab Hugh and put on the ring, the three of them will all travel back to England.
Beth and Patrick enter the Imagination Station and arrive in a thick forest. Beth and Patrick see Hugh a little ways off and attempt to sneak up on him. Hugh hears them coming, so Patrick and Beth explain that they are just trying to send him home and do what's right. Hugh doesn't want to go back, however, because he knows he will be arrested and imprisoned. He states that what Patrick and Beth think is right is not the same as what Hugh thinks is right. Hugh suddenly runs away. Beth and Patrick turn around and see several Native American warriors approaching them with drawn weapons.
The warriors grab the cousins, lead them to a Native American camp and shove them into a teepee. Inside the teepee is a Pilgrim boy named John, who explains that he is being kept as a prisoner. He got lost in the woods and was captured by warriors. A Native American man comes into the teepee and beckons for the three children to follow him. He takes them to the chief.
Chief Aspinet accuses them of being spies. John states that he simply got lost in the woods and couldn't find his way back to his village. Aspinet tells him that he never should have left his village and that John's people have caused the Native Americans great suffering. John protests that he and the others in his village want to be friends with the natives, but Aspinet points out that the villagers stole corn from his people and that friends should not steal from each other.
A small boat with John's father and a few other Pilgrim men approach the camp. The Pilgrims get out of the boat carrying their muskets and are faced by a line of armed Native American warriors. There is a tense standoff before the Pilgrims lower their weapons as a sign of peace. The Pilgrims and Native Americans begin trading, and Aspinet brings out the three children to use as bargaining tools.
Aspinet asks the Pilgrims' governor, a man named Bradford, what he will give in exchange for the children. Bradford offers Aspinet a steel hunting-knife, and Aspinet releases John. Bradford only has one more knife, however, which he trades for Patrick. Bradford offers a basket of beads, which is all he has left to trade, for Beth, but Aspinet refuses.
Beth offers him the golden mirror from Mr. Whittaker in exchange for her freedom. Aspinet accepts, and the Pilgrims leave with John, Beth and Patrick. As they board the boat, Aspinet reminds them that they still owe his people several baskets of corn.
As the boat arrives at the Pilgrims' village, a man rushes down the shore to meet them. He explains that Chief Yellow Feather's village has been attacked and that Squanto, who has been friendly to the Pilgrims, has been kidnapped. The Pilgrims have a treaty with Chief Yellow Feather that they will each fight for the other if necessary. Governor Bradford calls a meeting to decide what to do. Some don't want to fight for Chief Yellow Feather, but Bradford insists that it is their duty as Christians to honor the treaty. The Pilgrim men plan to leave on a rescue mission the next day.
Beth and Patrick decide that they should follow the men, believing that Hugh is probably involved in the kidnapping, but are stopped by John's father, who tells them to help with the chores. The rescue party returns with three badly injured Native Americans.
Beth helps the village doctor treat their wounds. She learns that Chief Yellow Feather's village was never attacked and that Squanto wasn't kidnapped. The three wounded natives were accidentally shot by the Pilgrims while they were searching for Squanto. Beth thinks that Hugh must have started the rumor.
As soon as their wounds are cared for, the Native Americans leave. The Pilgrims worry that Yellow Feather’s people will attack in retaliation, and they begin preparing for war. Patrick and Beth see John approach the military captain. John is distraught because someone stole his gun. He believes it was the Native Americans, but Patrick and Beth realize that it was probably Hugh.
Suddenly a scout brings the news that an army of Native Americans is approaching the village. The Pilgrims line up. They prepare to fire their muskets. A Native American fires a single arrow into a nearby tree. The arrow has a message attached to it that requests peace.
Squanto comes out of the woods with several other men and explains that the injured natives understand that the Pilgrims were simply trying to honor the treaty and rescue Squanto. The Native Americans and Pilgrims decide to hold a feast to honor the treaty and their friendship, which becomes the first Thanksgiving.
Patrick and Beth realize during the feast that since Hugh has a musket, he will want gunpowder and bullets. Patrick asks the Pilgrims' military captain if anyone is guarding the weapons store. The captain explains that John's father is keeping an eye on everything. After the feast, however, Patrick sees John and his father participating in a military demonstration, leaving no one to guard the storehouse. Patrick and Beth rush to check on it. Hugh is already there with his loaded musket.
Hugh threatens Patrick and Beth with the gun and demands that they return Mr. Whittaker's ring to him. Patrick gives him the pouch from Mr. Whittaker instead. Hugh explains his plan to take the musket back to his time in order to gain power. Hugh opens the pouch, which contains a ring belonging to Albert instead of the one from Mr. Whittaker. Hugh thinks it is the correct ring and puts it on, but since the ring belongs in medieval England, that's where Hugh ends up as well.
Patrick and Beth use Mr. Whittaker's ring to follow him. Hugh was unable to bring the musket with him, and he appears in a cave with Sir Andrew, who is a friend of Beth and Patrick's. Sir Andrew arrests Hugh and thanks Beth and Patrick for all of their help. Beth and Patrick then return to Whit's End and explain everything to Mr. Whittaker.