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?
In flashback, Duncan and Immortal Ingrid tackle the Nazis in 1935 Germany. In modern day, Ingrid has assassinated a Russian politician and Duncan wants to stop her from killing her next target, an American white-power advocate.
In flashback to 1867 Texas, Duncan is part of a posse after Immortal Koren and his gang of raiders. In modern day, Duncan's friend Immortal Cassandra is also after Koren, but she tells Duncan he is also Kronos, one of the Four Horsemen who brought terror and death to mankind through the ages. Meanwhile, Cassandra reveals Methos was also one of the Horsemen, which shocks Duncan into ending their friendship.