Immortal Walter Graham is trying to kill pre-Immortal Claudia Jardine, a brilliant pianist, so that she will remain young and at her creative peak forever. In flashback to England 1663, Duncan and Graham are traveling players, and Walter regrets his ability to recognize brilliance while lacking genius of his own. Meanwhile, Methos falls in love with Alexa and is devastated when Joe tells him she is terminally ill.
Duncan's Immortal friend Jim Coltec has killed one too many evil Immortals and has become the victim of a Dark Quickening. If Duncan has to take Coltec's head, will the Dark Quickening overpower him as well?
Duncan, still under the influence of the Dark Quickening, arrives in France. In flashback to 1917 France, Duncan is an ambulance driver and his Immortal friend Sean Burns psychoanalyzes the mental victims. In present day, Methos and Sean Burns try to get through to Duncan.
Duncan saves the life of President Hamad, a visiting politician, whose assistant is Immortal Kassim. But it turns out Kassim was arranging the assassination of the cruel Hamad to allow Nasir, descendant of the Moorish kings Kassim served, to take over the government. Now Kassim wants Duncan to kill Hamad in order to repay an old debt that Duncan owes him.
Magician Danny Cimoli is delighted to discover he cannot die and promptly incorporates being killed into his act. When Duncan tries to teach Danny about Immortals and defending himself, Danny doesn't take Duncan seriously.
In flashback to 1700's Scotland, Duncan and Immortal Warren Cochrane are among those fighting for Bonnie Prince Charlie. But only Duncan eventually realizes that the Scots must abandon the prince or be slaughtered in one mismanaged battle after another. In modern day, Goddard is paranoid and confused. He has forgotten he is Immortal. As Duncan helps him remember his past, he remembers that he blames Duncan for Charlie's failure to capture the Scottish and English thrones.
The de Valcourts are two Immortals who have been married, to each other, for two centuries. When their 300th anniversary turns into a marital battle and they separate, Duncan and Hugh try to get them together again.
Jack Shapiro tricks Joe into coming to Paris to face a Watcher trial. Duncan tracks Joe down, complicating Joe's situation even though he is trying to help. Meanwhile, Immortal Jacob Galati is tracking down and killing Watchers.
Continuation of "Judgment Day." The Watchers believe Duncan has been killing Watchers, with Joe's help. They are trying to kill both men, while Duncan tries to identify the real killer, another Immortal. In flashback to 1847 Europe, Duncan's Immortal gypsy friend Jacob Galati kills a mortal who raped Jacob's Immortal wife Irina, and he is promptly hanged by the gypsy-hating townspeople. In modern day, Jacob saves Duncan from a Watcher and tells him Horton's renegade Watchers killed Irina. Can Duncan and Methos stop the feuding before anyone else is killed?
In flashback to the Scottish highlands, a young Duncan hunts a wolf in a fey forest and finds Cassandra, an Immortal who is thought to be a witch by the Clan MacLeod. Back in modern San Francisco, Duncan and Cassandra reunite when Cassandra is convinced that Duncan is the one to fulfill an ancient prophecy, but her enemy Roland, an Immortal with the ability to hypnotize people as he speaks to them, is determined to finish Duncan before he can.
Richie is haunted by bitter dreams of Duncan trying to kill him, burying his fear by picking fights. Duncan is haunted by the need to eliminate his friendship with Watcher Joe. But when one of Richie's Immortal victims turns out to have been the protégé of Immortal Haresh Clay, Duncan and Joe between them may not be able to save Richie.
Immortal Carl Robinson has a great baseball career until he is seen killing another Immortal and forced to run for his life. He asks Duncan for help, but when another man is arrested for the murder, Duncan becomes Carl's conscience as Immortal police detective Matthew McCormick pursues Carl. In flashback to 1859 Louisiana, Carl is a runaway slave, again fleeing for his life. McCormick helps Carl but Carl eventually kills some slaver friends of McCormick's.
Duncan encounters Johnny K, who he last knew as a small-time hood during Prohibition. Since Johnny is now a professional assassin, he decides Duncan must die before he can identify Johnny. Meanwhile, Joe is flabbergasted when an old girlfriend appears in his bar and is apparently interested in rekindling the old flame.
Carolyn Marsh is a romance author whose latest book features the exploits of a hero named Duncan MacLeod and a villain named Terence Coventry, the name of another Immortal who Duncan knows -- and who Carolyn knows well. As Carolyn puts the moves on Duncan and tries to convince him to help promote the book, she gets into a catfight with Amanda. Meanwhile, Terence is furious at Carolyn for portraying him as a villain.
When Amanda disappears into a van after a robbery, Richie thinks she has been kidnapped and goes after her. He finds her with Cory Raines, an old acquaintance of Duncan's and Amanda's who has always brought them trouble. Unfortunately for everyone involved, the money that Cory stole belongs to a mobster, and he wants his money back. In flashback to 1926, Amanda leaves Duncan and their circus act to join Cory on a bank-robbing spree.
In flashback to 1880s San Francisco, Duncan's Immortal friend Alec mourns the murder of his young wife Genevieve by Kragen, but is convinced her spirit is still around. In modern day, Alec has been killed by Kragen, but his mortal widow Jennifer is convinced that Alec's spirit can't leave until Duncan keeps his promise to kill Kragen.
An Immortal "Messenger" preaches peace between Immortals to Richie, who tries to convince Duncan to stop taking heads -- right when Duncan encounters the Immortal former commander of Andersonville prison, where Duncan suffered part of the Civil War. Joe discovers that the "Messenger" has left a trail of dead Immortals behind him, when those he convinced of peace encounter those still fighting. Will Richie be the next victim?