An Immortal friend of MacLeod's is beheaded in his isolated mountain retreat where he had hoped - like MacLeod - to retire from the fight for a while. A brain-damaged, homeless veteran is charged with the grisly crime, and an attempt is made to link him to the killing of Slan Quince (the villain of episode one, 'The Gathering'), an Evil Immortal whom MacLeod himself had slain in combat. MacLeod must try and clear the innocent man and unravel the mystery of who killed his friend. Here again we get a glimpse of MacLeod's past, in flashbacks set during the American Civil War.

While visiting the courthouse to clear up Tessa's traffic tickets, MacLeod, Tessa, and Richie are among a group that is taken hostage by a band of men bent on freeing their leader, Slade, from imprisonment. When Slade's demands are not met, he chooses a hostage to sacrifice. MacLeod makes sure that hostage is himself, and returns from the dead to hunt down the gunmen one by one, as the police watch helplessly from outside.

MacLeod is struck and "killed" by a speeding automobile. When he revives in the hospital, he attracts the attention of a deranged doctor, who kidnaps MacLeod for his research on a miracle cure for trauma. When MacLeod escapes from the doctor, the doctor murders a potential witness and frames MacLeod for it.

A serial killer dubbed The Scalper' is attacking blonde women, including a friend of Tessa's. MacLeod recognizes the pattern of an Immortal who, betrayed by the woman he loved, became a killer. To end the carnage, MacLeod was forced to confront and kill him, back in 1925. Now the killings have started again, the modern day killer mimicking the 70-year-old M.O., killing in the same locations as the previous murders. It falls to MacLeod and Tessa to stop this madman.

Tessa witnesses the murder of a painter, Anne Wheeler, but the absence of a body leads everyone but MacLeod to doubt her story. MacLeod supports Tessa in her quest to obtain justice for Anne. It develops that Anne was killed by her Immortal ex-lover, to keep her from revealing his secret. After Tessa is taken to a police safe house, MacLeod realizes that the killer is in fact the Chief of Detectives, and he must rescue Tessa and bring justice to Anne's killer.

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.

A day at the circus reunites MacLeod with a former lover, the Immortal femme-fatale, Amanda, who has always meant big trouble for him. Amanda, meanwhile, is in trouble of her own as her former partner, Blaine, has escaped from prison and wants her head. She plays the two Immortal men against each other, drawing MacLeod into a daring, high-stakes burglary she and Blaine are plotting.