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.

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.

Richie returns, on the run, turning to MacLeod for help. An Immortal has been following him, refusing to confront him, but committing grisly murders wherever Richie goes. Richie is arrested for the murders. Mac learns that Immortal hunter Martin Hyde is behind the murders: considering the Quickening of a green Immortal like Richie not worth the taking, Hyde has been hounding him in order to drive him to his teacher. MacLeod must clear Richie of the murders and defeat the evil Immortal.

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.

MacLeod feels the Buzz coming from an ancient sarcophagus and opens it to find Nefertiri, Cleopatra's handmaid, buried 2000 years ago with her mistress. Now revived, she pursues a vendetta against the Immortal Marcus Constantine, who was her lover and her enemy. Mac believes Constantine, who claims that he no longer wishes to fight Nefertiri — this former Roman General has turned his back on battle and is now a curator, working to preserve history and its lessons. But Nefertiri can't let go of the old grudge, and for the first time, MacLeod is forced to face a woman he loves in Immortal combat.