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.

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.

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.

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.

Pete Wilder just saved Richie from an attack by some guys wearing Watcher tattoos. Or did he? Nothing is what it seems, and MacLeod becomes increasingly wary of Pete, despite Richie's protests that the guy is his friend. When MacLeod's mistrust gets the possibly innocent Pete killed, Mac becomes increasingly unsure of himself. Unknown to MacLeod, his old enemy Horton is pulling all the strings. Horton is secretly training escaped killer Lisa Halle to go after MacLeod while he's troubled and vulnerable.

Joe Dawson arrives in Paris to let MacLeod know that Horton may still be alive and coming after him. However, when MacLeod meets Lisa Milon, a dead-ringer for Tessa (Lisa Halle after plastic surgery), all thoughts of Horton and the Watchers go out of his head. Richie, unsure if Mac is thinking clearly, goes to Dawson for help and winds up taking a bullet for him when Horton tries a hit. Lisa is kidnapped, and MacLeod insists on going after her even though his friends warn him it may be a setup. He can't take a chance on burying her again. When Lisa finally tries to kill MacLeod, he turns the tables on her and Horton at long last gets what's coming to him.

The popular series lays down its sword after six seasons in this stirring finale, in which MacLeod makes the ultimate sacrifice to save the lives of Amanda and Joe Dawson... then reunites with old friend Hugh Fitzcairn, and gets a look at what the world-- and his friends' lives-- would be like without him.

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.