MacGyver and Pete go to meet with Pete's friend, Irwin Malcolm. Pete has asked him to trace MacGyver's family roots, and Malcolm has learned that MacGyver is possibly related to the McIver clan. The McIver and MacGyver clans both date back to 14th century England, and both had sons of the era that shared MacGyver's first name. Researching further, Malcolm has learned that in the 7th century, Ian McIver fell victim to a great evil and was imprisoned in a dungeon. Ian's son also bears the same first name as MacGyver.
As they leave, MacGyver is skeptical of Malcolm's clan but Pete insists that his friend's research is authentic. MacGyver notices a groom and his best man outside of a church, and two workmen moving a mattress on the fire escape above. The mattress grazes a flower box, sending it tumbling toward the groom. MacGyver leaps at the groom and shoves him out of the way, but the flower box hits him in the head.
MacGyver wakes up and discovers medieval knights standing over him. He realizes that he's in the middle of a jousting lane in the middle of the countryside, and rolls out of the way as the two sparring knights strike each other. Duncan, the Black Knight, takes down Galahad, his opponent. Duncan moves in for the kill and Galahad is unable to defend himself because of a broken arm. MacGyver steps between the two and asks what's going on. Duncan explains that they're in Camelot and MacGyver insists that if Galahad dies, history will be irrevocably altered. The king's sorcerer, Merlin, steps out and asks if MacGyver is a magician from a foreign land. He accuses MacGyver of consorting with demons but Duncan dares MacGyver to second Galahad. MacGyver agrees but refuses Galahad's offer of a weapon and armor. He borrows a nearby rope and rides at Duncan. When the knight tries to strike him, MacGyver swings over the side and avoids the thrust. On his next pass, MacGyver lassos Duncan and drags him to the ground.
The balladeer sings MacGyver's praises and everyone present is impressed... except Merlin, who is upset that he's been upstaged by MacGyver's "magic." King Arthur makes his entrance, and MacGyver is surprised to see that he looks just like Pete. Just like Pete, Arthur is nearly blind, due to an ambush launched by Queen Morganna. Arthur calls MacGyver forward and is happy to hear that Galahad is still alive, but disappointed that his knights are fighting among themselves. He tells the assembled knights that Morganna has developed a new weapon that can kill from great distances, and asks if any of them will venture forth to rescue the captured lady, Cecelia. Galahad speaks for MacGyver, introducing him to the king. MacGyver is unable to explain how he came there or what's going on. When Arthur asks for his name and MacGyver responds, the assembled knights draw their weapons and prepare to attack. Arthur tells them to halt and explains that Ian McIver has allied himself with Morganna against Camelot. MacGyver refuses to believe it and explains that he comes from a future time where he has knowledge that McIver is falsely accused. Merlin tries to turn the others against him, insisting MacGyver is evil, and Duncan is glad to kill the man who defeated him.
Arthur tells the knights to stop and calls upon Merlin to test his magic against MacGyver's to see which is the stronger. Merlin goes first and uses a simple rope trick to impress the knights. MacGyver notices the invisible threat and uses his Swiss Army knife to cut it, causing the rope to drop to the ground. Arthur asks for a demonstration of the magic of creation and MacGyver uses a match to "summon" fire. Impressed, Arthur asks MacGyver to go forth and rescue Cecilia. Merlin intervenes again, insisting that by law, a knight must accompany a wizard. Duncan steps forward to volunteer but Arthur has someone else in mind. However, before he can choose the knight, he collapses. MacGyver has the knights get Arthur into the king's tent and starts looking around while Merlin uses his magic. It has no effect, but MacGyver discovers a discarded vial and a meat knife covered with a bit of the liquid found in the vial. Working quickly, MacGyver mixes eggs with what's left of the poison to create a neutralizing agent to cure Arthur.
The knights remember that a new page handled the food and go to look for him, while Merlin secretly takes the vial. Arthur asks to talk to MacGyver in private, and explains that he wants to knight MacGyver so that he can ride out with Merlin, rescue Cecilia before she is used as Morganna's test subject, and rescue Ian McIver.
Duncan finds the new page and searches him. They find gold on him and Duncan takes that as an admission of guilt and kills him. MacGyver is shocked at the brutal justice and suspicious of Duncan's actions. The knights show Arthur the gold, and the king realizes that it belongs to Merlin. They shove Merlin forward and Duncan says they found him washing out the vial of poison. Merlin explains that the vial is his and someone stole it. However, they have also found a parchment with Merlin's seal on it, telling the page to poison Arthur. Merlin claims that someone stole his seal along with his gold, but only MacGyver has any doubts about his guilt. Duncan calls for a trial and Arthur has no choice but to agree. As Merlin is taken away, MacGyver tells Arthur that Merlin is innocent and he'll find the proof he needs to clear the wizard's name.
That night, Duncan begins the hearing while MacGyver slips into Merlin's tent. The wizard is being kept prisoner there and MacGyver tells him that the poison that was used on Arthur was a binary substance that Merlin couldn't have invented in the 7th century. He uses Merlin's workshop to build a crude battery and use electricity to separate the poison into its two components. He works through the night and in the morning, confirms that one of the ingredients was vanadium, a substance that won't be discovered for a thousand years. Outside, Duncan ends the trial and the knights come to get Merlin. As they arrive, MacGyver asks about Scotland and Merlin confirms that the country is under Morganna's control. When the knights take Merlin away, MacGyver tries to intervene and Duncan knocks him to the ground.
MacGyver goes to see Arthur and tells him that vanadium is only found in Scotland. Arthur confirms that only one knight has been in Scotland recently: Duncan, who traveled there a week ago to prove his courage. Arthur gives MacGyver the royal seal so that he can stop Merlin from being burned at the stake.
While Merlin stalls for time and pronounces his curse on the assembled knights, MacGyver goes to Merlin's tent, grabs some chemicals, and mixes them in a water bag. As the bag starts to swell, MacGyver rides toward the pyre. Duncan finally ignites the pyre but MacGyver arrives and uncorks the bag. He uses the chemical spray to put out the fire and show the knights the royal seal. MacGyver tells them that Duncan is the killer, and obtained the vanadium-based poison while in Scotland. Duncan panics and attacks MacGyver, proving his guilt, and then rides away before anyone can stop him.
Later, MacGyver and Merlin prepare to depart for Morganna's lands to rescue Cecilia. MacGyver has changed into a knight's garb but refuses to carry weapons or armors. He does accept the royal favor from Arthur, a piece of paper within a small metal cylinder on a necklace. The unlikely pair ride north into Scotland and find the cave entrance that leads to Morganna's castle. They dismount and go inside, avoiding smoking fumaroles.
They hear Duncan cry out from up ahead, claiming that he injured himself when his horse threw him. Merlin refuses to accept MacGyver's suggestion that it's a trick and barrels on ahead. MacGyver follows him and the two fall through a platform on a pivot point. MacGyver manages to grab the platform as it swings to a stop perpendicular to a pit of lava, and Merlin grabs MacGyver. Duncan emerges to boast of his triumph, but Morganna emerges behind him and shoves him into the lava. She chuckles and suggests that MacGyver let go if he finds holding on too difficult, and walks away. As MacGyver tries to maintain his grip, the slat he's holding onto starts to crack...
(to be continued)