After Midori Koto sees her husband, rich industrialist Michael Kent, murder her lover, she kills Kent and runs to MacLeod for protection. She reminds MacLeod of a vow of protection his ""ancestor"" (actually MacLeod himself) made to her family over 200 years before. Flashbacks tell the story of MacLeod coming to the aid of the samurai Hideo Koto after MacLeod is shipwrecked in Japan. Hideo befriends MacLeod -- even though the penalty for helping a ""barbarian"" in isolationist Japan is death. When Hideo is forced to commit ritual hari kari by his feudal overlord for that crime, MacLeod serves as his second. He vows to Hideo he will always protect the Koto family and is bequeathed the dragon head katana sword he uses to this day. Back in the present, MacLeod discovers that Kent is an Immortal and he's still alive. In order not to further dishonor her family's name, Midori returns to Kent. Kent challenges MacLeod, who fulfills his vow to the Koto family and frees Midori from her loveless mar

In the 1600s, MacLeod sought refuge for a time in a monastery founded by Paul, another Immortal. There he encountered Kalas, an Immortal monk with a heavenly singing voice. When MacLeod discovered that Kalas was routinely taking the heads of Immortals as they left the sanctuary, MacLeod and Paul expelled Kalas from the monastery, separating him from the music that was his life. Now in the present, Paul and his choir have been lured out of their monastery for a concert tour. When Paul disappears after a concert, MacLeod discovers that Kalas is after his revenge. Meanwhile, two mysterious deaths at the hospital seem to be linked to negligence on Anne's part. Later, when drugs are found in Joe's bar, it becomes obvious that Kalas is trying to destroy MacLeod's friends before coming for him. MacLeod confronts Kalas and finds that Kalas is a strong and skillful fighter, better than MacLeod has faced before, and is nearly the victor. To save himself, MacLeod throws himself off the concert ha

MacLeod is picked up at the airport in France by his old friend, Hugh Fitzcairn. For the first time in the 350 years MacLeod has known him. Fitz has settled down as a Universitv Professor with the love of his life, Naomi. Flashbacks show MacLeod and Fitz's first meeting, when MacLeod was protecting the Doge's daughter from Fitz's amourous advances in Venice, 1637. When Naomi's jealous ex-lover is found strangled next to a computer displaying Fitz's falsified teaching credentials, Fitz goes on the run from the police. MacLeod realizes that Fitz is being framed by Kalas, who has followed him from the U.S. Kalas challenges Fitz and takes his head while MacLeod watches, unable to interfere.

When two Watchers end up dead by Kalas' hand, Joe realizes that Kalas is looking for Methos, the mythical ""oldest Immortal."" MacLeod knows that, with Methos' quickening, Kalas would finally be strong enough to defeat him. Kalas and MacLeod race to be the first to find Methos. Meanwhile, Richie muscles his way onto a top level motorcycle racing team and the champion, Basil, starts to get nervous. Flashbacks are to Paris in the 1920s, when Kalas, then known as Antonio Neri, was the toast of the opera world. When Kalas threatens a young girl in MacLeod's protection, they fight. Kalas escapes, but not before MacLeod inflicts a throat wound that destroys Kalas' vocal chords and the singing that has been his life since the Middle Ages. Kalas nearly takes Methos in battle and, realizing that he will not be able to defeat Kalas, Methos offers his own head to MacLeod. MacLeod refuses and challenges Kalas on his own, nearly defeating him when the police arrive to send Kalas to prison for the dea

McLoud bought a Celtic bracelet once given to the love of his mortal life and after her tragic death he buried it with her. He returns to Glen Finnin to return the bracelet to her grave and learns of several gruesome ritualistic killings based around the one immortal who killed Mac's father. Naturally Mac must get to the bottom of the killings and keep his head in the process.

MacLeod knew him as Melvin Koren, a desperado who left a trail of death and fire across the Old West, but Cassandra remembers him as an evil far older. He is Kronos, leader of the Four Horsemen, mounted Bronze Age raiders who murdered, raped, and pillaged their way across two continents. Never was a band of Immortals more cruel or more feared. He destroyed Cassandra's people and she's been hunting him across the millenia. But Kronos has a different target now -- Methos.

In 1944, Ingrid Henning had the chance to kill Adolf Hitler and failed. She's been atoning for that failure ever since by killing dictators, tyrants, racists, and fascists who might have the potential to become as dangerous. MacLeod has a chance to stop her before she kills more mortals, but by stopping her, does MacLeod commit the same evil for which he's judged her guilty?

MacLeod's old compatriot Hugh Fitzcairn comes to town bearing a mystery -- some of their other Immortal friends have disappeared suspiciously. MacLeod realizes that someone may be following Fitz, and realizes too late that Fitz has put Darius in danger by visiting him. Finding Darius dead in his chapel and Fitzcairn kidnaped, MacLeod won't rest until he finds the men responsible. Tracking the killers of his old friend, MacLeod discovers that there is a band of mortals hunting Immortals, and even holy ground is no protection from them. MacLeod finds the renegades in time to save Fitzcairn and confront James Horton, leader of the Hunters, but Horton eludes his grasp.

A mortal named Pallin Wolf, one of the renegade Watchers who believes the Immortals must be eliminated, lures an Immortal to his house and kills him, getting the advantage by tricking him into a sealed room that is completely dark, then stalking him with night vision goggles. Meanwhile, a Gypsy fortuneteller they meet in a restaurant, Greta, warns Tessa that she is in danger. When Tessa is kidnapped by Wolf, MacLeod returns to Greta, asking for her help. But she's mostly a hustler, and not accustomed to getting actual visions, so the clues she is able to provide are meager. Finally, Mac finds Wolf's house, where Wolf is waiting for him. He meets Wolf in the dark room and all seems hopeless until he remembers a matchbook Greta gave him with her phone number in it. Lighting the matches, he regains the advantage and kills Wolf. However, as Tessa and Richie are heading for the car, a young junkie accosts them for money, and in an act of senseless violence, shoots them both. As Mac mourns,

As Charlie regains strength, MacLeod accepts help from Dawson one last time, and barely misses catching Xavier and Horton. He then follows their trail to Paris -- accompanied by the persistent Renee Delaney. They track down Horton, and when he almost escapes, he is shot by Joe Dawson. MacLeod, with the help of his humorous new neighbor Maurice, then tracks down Xavier and finally takes his head. In a coda, however, we learn that Horton still lives.

Fitz died three hundred years ago... Horton has taken over the Watchers... Joe Dawson has been reduced to a bitter, penniless vagrant... Amanda is a black widow... and Methos has rejoined the Horsemen to avenge his fiance's death. If you think that's bad, just wait till you find out what's happened to Richie and Tessa.

Warning comes from MacLeod's old friend Darius, a monk over 2000 years old, that Grayson, Darius' one-time protege, is now stalking Darius' other students -- among them, possibly, MacLeod. Grayson, disillusioned that his former comrade-in-arms has become a man of peace, is killing Darius' mortal students in order to draw the monk off holy ground and into combat. MacLeod must protect peace activist Victor Paulus, another of Darius' students, from Grayson's plot to assassinate him. Later he joins Richie and Tessa in France where they will live while Tessa takes up her new job as curator of a traveling collection.

Xavier St. Cloud returns, killing Immortals with the help of mortal mercenaries who shoot his prey, making his kill easy. His next target is MacLeod but, warned by Dawson, Mac and Charlie just manage to escape death -- though the dojo is all but destroyed in the gunfight. Renee Delaney, a CID agent investigating the mercenary angle, gets on the case. MacLeod goes after Xavier himself, and Charlie insists on coming along. During his battle with St. Cloud, MacLeod spots James Horton, the Hunter who killed Darius. Distracted, Mac is 'killed' and falls down an elevator shaft out of beheading range, and Charlie is badly wounded and lies near death. Blaming Dawson for helping Horton escape alive, MacLeod warns him not to cross his path again.

MacLeod arrives in France, leaving a trail of hate and destruction in his wake. Methos finds him and discovers just how evil MacLeod has become when he tries to take Methos' head on holy ground. After MacLeod kills another good friend, Methos realizes that the only way to save MacLeod may be to kill him.

When MacLeod was but a wee lad in the village of Glenfinnan, he thought Cassandra, the Witch of Donan Woods, was only a myth, a fairy tale concocted by crafty old men to frighten unwary children-- until the night she found him alone in Donan Woods. Now, four hundred years later, Cassandra comes to MacLeod again, this time to tell him of his role in an ancient prophecy -- that only Duncan MacLeod can challenge and defeat the voice of darkness.

Determined to investigate the death of his old friend Darius, MacLeod follows a lead back to his old stomping grounds in the Pacific Northwest. He meets Joe Dawson, a bookstore owner with a secret; he soon learns that Dawson is a high-ranking member of an ancient secret organization known as The Watchers, who observe and record the lives of the Immortals, passing their archives down from generation to generation. Unbeknownst to Dawson, his brother-in-law, James Horton (the man who killed Darius), has been recruiting Watchers to kill Immortals. We are left with the knowledge that other renegade Watchers may be waiting to try for MacLeod's head.

Dawson's life is on the line when the Watchers try him on the charge of treason for his friendship with MacLeod. Watcher deaths have risen dramatically since Dawson first told MacLeod about the Watchers and the Tribunal is determined to punish Joe and stop the killing. MacLeod and Dawson argue his case, but even as the trial goes on, the Watcher killings continue.

When her mentor Rebecca is killed, Amanda is determined to avenge the death, even though it means going up against the formidable Immortal Luther, and very possibly losing her head. She comes to Mac for a final fling before her likely death, and when he discovers that she's after Luther, he tries to take the battle on himself, feeling he has a better chance of survival. Together they discover that Luther is hunting the pieces of an ancient crystal that Rebecca divided among her students, believing that the whole crystal will make him invulnerable and ensure that he is the Last Immortal. In the final confrontation, both Amanda and MacLeod take their turns battling the ascetic Luther.

The people of a tiny Balkan nation are rising up in arms against an oppressive dictator. The freedom fighters are led by Paul Karros, a vibrant, charismatic leader. Karros is an Immortal who once served as a slave under Roman oppression and fought his way to freedom with Spartacus. Since that time, whenever the common people have been fighting against oppression, Karros has been at their side. Karros and his assistant, Mara, have come to the U.S. to drum up support for their cause. MacLeod and Karros fought together in the Mexican Revolution and Karros tries to convince MacLeod to fight with him in this just cause. MacLeod turns him down, but Charlie is tempted both by the cause and by Mara. When Father Stefan, a local liaison, is critically wounded in an assassination attempt, MacLeod realizes that Karros is determined to fight the war at any cost -- even at the cost of sabotaging peace negotiations by killing those who trust him. When Mara discovers the truth, she threatens to expose

Dawson has a new girlfriend, art historian Lauren Gale, and a new attitude on life. Unfortunately, Dawson arrives at Lauren's house one evening to witness her murder. We discover the murderer is Armand Thorne, benefactor of the Thorne Museum of Antiquities, who was being investigated by Lauren. MacLeod finds an ancient gold cross on display in Thorne's museum, a cross that had been stolen out from under his protection nearly two hundred years before. Armand Thorne, MacLeod discovers, is actually John Durgan, the Immortal trapper who murdered a frontier priest and stole the cross. MacLeod persuades Amanda to come out of cat-burglar retirement and help him to steal the cross from the museum in order to lure Thorne out of his heavily protected fortress. MacLeod confronts Thorne, taking his head, and finally gets fulfill his promise to return the Cross of St. Antoine.

Michelle Webster, the rebellious teenage daughter of a friend of MacLeod's, drives away from her parents' house in a rage and right over a cliff. Trauma surgeon Anne Lindsey tries her best to save Michelle, but it's too late. MacLeod rushes to the hospital to comfort his grieving friends -- and sneak their newly Immortal daughter out of the morgue. He tries to train her in the arts of Immortality, but Michelle just wants to have fun. She meets Immortal Axel Whittaker who promises her all the fun and adventure she could imagine if she stays with him. In flashback, we see that Axel uses beautiful new Immortal women as bait to trap other Immortals and take their heads -- MacLeod barely escaped with his in 1896 Boston. Axel uses Michelle to lure MacLeod to his yacht, where they continue the battle they started a hundred years before. MacLeod defeats Axel. Michelle, witnessing the fearsome power of the Quickening, agrees to be trained as an Immortal under the protection of Amanda.

Cullen, an old friend of MacLeod's, is burnt out from centuries of playing The Game and has turned to drugs and alcohol to get the courage to keep on playing. Cullen had a run-in with Richie and now he's coming for Richie's head. While playing ""chicken"" with Richie on a mountain road, Cullen crashes head-on into a bus full of passengers, killing many. MacLeod tries to convince Cullen, who he once knew as the greatest of the warriors, to stop using the drugs, but a paranoid Cullen believes MacLeod is just trying to render him helpless. Finally, MacLeod has no choice but to confront his former comrade and defeat him.

What happens to a kid who hits Immortality before he hits puberty? MacLeod and Richie take in 10-year-old Kenny, who asks for their protection after the fatherly Immortal who was protecting him is beheaded. Kenny, we discover, is not the sweet little lamb he appears to be. He has been Immortal for nearly 800 years, and has survived all that time by convincing other Immortals to take him in and protect him -- and then taking their heads. Kenny tries to get MacLeod, but he is continuously thwarted by the presence of Anne. Kenny attempts to get Anne out of his way, but MacLeod, realizing the truth about Kenny, manages to rescue her. He goes after Kenny to stop him from killing again, but Kenny manages to escape by blending in with a group of innocent children.

Immortal David Keogh, once an indentured servant, is a noted craftsman with his heart set on marrying his sweetheart, Jill. Unfortunately, Jill does not agree. Although she loved Keogh once, she was unable to handle it when he confided the secret of his Immortality. Now Keogh won't leave her alone and she's coming to MacLeod, whom Keogh respects and might listen to, for help. But Keogh won't listen, convinced that Jill needs him as much as he needs her. In flashback, we see a time in MacLeod's life when he, too, was obsessed with a woman he couldn't have. When Jill is killed in a tragic accident while trying to get way from Keogh, Keogh blames MacLeod and swears vengence.

MacLeod is tormented by visions of his own death, beheaded by a mysterious dark-hooded figure. Anne tries to convince him to seek medical help, but instead he turns to his old friend Garrick, who has spent centuries studying the mind. MacLeod saw Garrick in the 17th Century, when MacLeod barely escaped being burned as a witch. What MacLeod didn't know was that Garrick was not able to escape as well. Garrick convinces MacLeod that the dark-hooded figure is a racial memory that haunts all Immortals and that the way to defeat it is to not fight it, to accept it for what it is. When MacLeod, haggard and exhausted, faces the specter for the last time, puts down his sword and refuses to fight it, the figure goes for MacLeod's head -- until at the last moment MacLeod realizes the figure is Garrick, seeking his revenge after all these years. In the Tag, Anne, frustrated that MacLeod won't open up to her despite their intimate relationship, leaves him.