MacGyver and Pete go to a genealogy store to meet with Pete's friend Irwin Malcolm. He traces the MacGyver clan back to the McIver clan and claims that one stemmed from the other. Ancestors in both dating back to the 14th century gave their sons the same first name as MacGyver. The lineage goes even further back to the 7th century where there are references to an Ian McIver who fell victim to a great evil and was imprisoned in a dungeon. That Ian's son also shares MacGyver's first name.
Outside, Pete explains that Irwin is authentic. MacGyver notices workmen moving a mattress on a fire escape above two men preparing for a wedding. The workmen knock a flower box off the balcony and MacGyver shoves the two men out of the way. The flower box lands on MacGyver's head, knocking him out.
MacGyver wakes up to find himself lying in the dirt surrounded by men in medieval garb. He discovers he's in the middle of a jousting lane and quickly rolls out of the way as the two knights slam together. The knight in black, Duncan, downs the other knight, Galahad. Duncan dismounts and tells Galahad to fight or die. Galahad's arm is broken and MacGyver intervenes. He asks who they are and where he is. Duncan tells him he's in Camelot and MacGyver insists he can't kill Galahad because it'll screw up history. Merlin arrives and wonders if MacGyver is a sorcerer from a foreign land. He warns Duncan that there is demon magic about. Duncan is unimpressed and asks if MacGyver wants to second Galahad. Given the alternatives, MacGyver agrees to second Galahad, who offers his armor. MacGyver declines and refuses to fight with a weapon. He borrow a rope and mounts, and then prepares as Duncan charges at him. MacGyver hangs off the side of the horse and avoids Duncan's first thrust. When he comes around again, MacGyver ducks and then lassos the knight, bringing him to the ground.
The knights congratulate MacGyver but Merlin dislikes the development. As the balladeer sings MacGyver's praises, King Arthur enters. He bears a strong resemblance to Pete Thornton and is also blind. Galahad explains that Queen Morganna raided the lands and Arthur lost his sight in an ambush. Arthur calls MacGyver forward and admits he has enough trouble without his knights fighting among themselves. He warns that Morganna has created a new and powerful weapon that can kill from a great distance. Arthur calls upon knights to rescue Cecilia and then asks Galahad to speak on MacGyver's behalf. The knight speaks glowingly of his new friend and MacGyver admits he's not sure how he came there. When he says his name, the knights draw their weapons and Arthur tells them to back down. Arthur explains that the McIver name is banished upon pain of death because Ian has allied himself with Morganna, and they hold Cecilia prisoner. MacGyver insists his ancestor has been wrongly accused and admits he has knowledge of a future time. Merlin objects and says they must purge the evil among them. Duncan and the other knights draw their swords but Arthur orders them to hold. He tells Merlin to show his magic first and then they'll put MacGyver to the test.
Merlin reluctantly agrees to test his magic and uses flash powder to drive the knights back, and then places a rope on the ground and causes one end to levitate. MacGyver, unimpressed, produces his Swiss Army knife and cuts the invisible thread Merlin is using to rise the rope. Merlin insists it's demon magic but Arthur asks for a demonstration of magic of creation. MacGyver uses a match to create fire and Arthur declares him worthy to go forth and rescue Cecilia. Merlin asks that a knight accompany him and Duncan points out that the law requires a knight must go forth with the wizard. Duncan is eager to volunteer but Arthur has an idea. He collapses in mid-sentence and MacGyver has the knights help him get the king to his tent. Merlin insists on curing him with his magic and MacGyver explores the tent. He finds a discarded vial and a meat knife covered with poison. MacGyver shoves Merlin aside and mixes eggs with poison to produce an antidote.
As Duncan and the other knights go to look for the new page that handled the food, Merlin secretly pockets the vial. Arthur orders Merlin out and then insists that MacGyver is virtuous and valorous, and explains that Morganna will test her new weapon on Cecilia. He wishes to make MacGyver a knight so he can ride out with Merlin, rescue the damsel, and rescue his ancestor.
Duncan captures the page and finds gold upon him. The page admits the gold is his and Duncan stabs him through the chest before MacGyver can stop him. Satisfied, the knights return back to the king and report what happened. Duncan shows Arthur the gold and the king realizes that the gold belongs to Merlin. The knights bring Merlin in and he appeals to Arthur. Duncan accuses Merlin of being the traitor and explains that they found Merlin washing out the vial. Merlin says that the vial was his and was stolen. They also found a parchment bearing Merlin's personal seal giving the page the order to kill Arthur. MacGyver wonders when Duncan found the letter, and Merlin feebly claims that someone stole his seal when they stole his gold. Duncan calls for a trial by the knights and insists they have no choice, and Arthur reluctantly agrees. Once the wizard is taken away, Arthur wonders how it could have happened. MacGyver believes Merlin is innocent and asks permission to use the wizard's supplies to prove Merlin's innocence.
That night, Duncan begins the trial while MacGyver enters Merlin's tent where he's tied to a pole. MacGyver explains that the poison was applied to the mutton and then activated by exposure to wine. He doesn't believe Merlin could have made it. MacGyver builds a crude battery to separate the components of the poison. By morning he has completed his work and determines that the poison contains vanadium, a binary poison that couldn't exist for another thousand years. The knights conclude the trial and arrive while Merlin confirms that Scotland is Morganna's land. The knights take Merlin away and MacGyver tries to intervene, but Duncan knocks him down and rides off to prepare Merlin for execution.
Merlin runs to Arthur's tent and explains to the king that vanadium could only be found in Scotland. Arthur realizes that none of his people have been there except Duncan, who journeyed there a week ago as a symbol of his courage. Arthur gives MacGyver his royal seal for authority as he goes to stop Merlin from being burned at the stake. Duncan prepares the pyre and orders the knights to light the fire. They hesitate as Merlin pronounces his curse.
MacGyver stops at Merlin's laboratory to collect some chemicals and mix them in a water bag. He then rides off to the pyre where Duncan has finally had enough and lights the pyre himself. MacGyver rides up and uses the chemicals and the water bag to put out the fire. When Duncan prepares to relight the torch, MacGyver shows the royal seal and insists that Duncan is the assassin. He lays out the evidence and Duncan attacks him, convincing the knights of his guilt. He hastily rides away before the knights can capture him.
Later, the balladeer sings of how Merlin and MacGyver will be riding off to rescue Cecilia. MacGyver dons local garb but refuses to take armor or weapons. Arthur gives him the royal favor, contained within a small metal cylinder on a necklace. Merlin and MacGyver ride into Scotland and find the cave that gives entrance to her lair. They proceed on foot into the cave, which contains sulfuric fumaroles. They hear Duncan cry out, saying his leg is broken after his horse threw him. An angry Merlin starts to stalk off and when MacGyver warns that it's a trap, Merlin shrugs him off and goes on and MacGyver follows him. They step onto a wooden platform that rotates downward, dumping them into a pit of lava. MacGyver manages to grab the platform and Merlin grabs MacGyver. Duncan emerges to boast of his triumph, but Morganna comes up behind him and shoves him into the lava. She advises them to let go it if becomes too hard to hold on and departs. MacGyver tries to climb up the slats as they break under their combined weight...
(to be continued...)