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.

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.

MacLeod stumbles across the trail of an Immortal, Xavier St. Cloud, who has lived in hedonistic splendor down through the ages by remorseless robbing and killing innocent men and women. MacLeod had nearly fallen victim to this remorseless killer behind the front lines during World War One, when Xavier used poison gas to loot a payroll truck. He uses even deadlier gas in modern day Paris, and MacLeod must track him down before he kills again. He succeeds in defeating Xavier, but the Evil Immortal escapes with his head. In a humorous yet touching subplot, Richie falls for a glamorous older woman, not realizing she is married, and Tessa must disentangle him from the woman's clutches.

Grace Chandel has been a Good Immortal, working for the betterment of mankind as a midwife, doctor, and scientist over the centuries. Her one weakness is another Immortal, Carlo Sendaro, a former lover who is obsessed with her and refuses to let her go. He slays Grace's current (mortal) lover and, when she refuses to run off with him, frames her for the killing. She turns to her old friend Duncan MacLeod for help.

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.

When fatal stabbing fails to kill him, Alfred Cahill becomes convinced that he has been chosen by a higher power to wage a crusade against 'perversion', and cuts a bloody path through Paris, murdering prostitutes and pimps, and endangering an old friend of Tessa's who has become a call girl. MacLeod tries to explain Immortality to Cahill, but he can't get through to him, and finally is forced to take his head.

An Evil Immortal, Kuyler, has hired himself out down through time as an assassin -- the most successful killer in all of history. He strikes again in modern day Paris using his signature disguise as a mime. A French Police Detective, LeBrun, suspects that Duncan MacLeod is connected to Kuyler, but of course he cannot imagine that Kuyler once killed an eighteenth-century baron under MacLeod's protection. When LeBrun is wounded protecting Tessa from Kuyler's men, MacLeod confronts the Immortal assassin and puts an end to his centuries-old reign of terror.

Seeking revenge for the apparent death of her lover, Walter Reinhardt, Rebecca Lord toys with MacLeod before she attempts to kill him with Reinhardt's sword. Rebecca knows nothing of Immortals or their combat, and she believes MacLeod murdered Reinhardt. Unbeknownst to her, Reinhardt is still alive, and is using Rebecca in a cat and mouse game to draw out MacLeod for their final confrontation.

Duncan McLeod is roused from his peaceful existence with the love of this life, Tessa Noel, when he is challenged to Immortal combat by Slan Quince, an Evil Immortal. An old friend and Clansman, Connor MacLeod, comes to try and convince Duncan to once more join the fray in the battle of Good versus Evil. This episode also introduces Richie Ryan, a kid from the streets whom Duncan befriends after catching him breaking into his antique store.

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.

When Tessa is taken by a band of Survivalists who live off the land in the vastness of the Pacific Northwest, MacLeod must call on all of his own skills, honed a hundred and fifty years earlier, when he roamed this same mountain fastness. The leader of these modern day mountain men, Caleb (who is revealed to be an Immortal), falls in love with Tessa, and in the end he and MacLeod battle to the death, axe against sword, against the primitive backdrop of the timeless wilderness.

Richie meets a beautiful young woman who leads him into the world of haute couture. His youthful jealousy causes him to run afoul of a world-class fashion designer, a deadly Immortal.

When the stepdaughter of an Immortal is raped, the Immortal comes after the young man. MacLeod, a guest in the home of the accused boy's father, feels he must protect the family from this unstoppable menace. He urges the Immortal to see due process done, but the man has no interest in listening to reason, and he lays siege to the house.

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.

Richie Ryan tries to protect an old girlfriend, Nikki, from a band of drug dealers. This puts them both in jeopardy from an Immortal, Voshin, whom MacLeod knows from an adventure during the Second World War when he was trying to smuggle Jewish refugees out of occupied Eastern Europe. Nikki complicates the story by withholding drug money she has stolen from the gang, thinking she can use it to make a better life for her small daughter. Tessa, meanwhile, becomes enamored of the child, raising issues for her and MacLeod.

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.

A mysterious death at the Paris Opera re-acquaints Duncan MacLeod with one of the strangest Immortals he has met in his many travels over the centuries. Ursa is a hulking giant -- more beast than man -- who Duncan rescued from persecution centuries ago, delivering him to sanctuary in an abbey. The abbey has long since been destroyed and Ursa now lives under Paris. He has become enamored of a past-her-prime opera singer who tries to use Ursa's innocent soul to murder her rival.

Richie falls for a con man's ploy when he attempts to find out more about his parents, whom he has never known. The con uses Richie for a place to crash and anything else he can get out of him by pretending to be his father. MacLeod also relives his past in the memories of first becoming immortal and being cast out of his clan by his father.

A deadly herbal drug takes the life of Richie's friend, and MacLeod suspects the source of the drug is another Immortal, Kiem Sun, who has long sought to perfect such a drug and remove its lethal side effects for the betterment of mankind. But a disciple of Kiem Sun's is using the drug for his own gain, and MacLeod and his old friend must track him down. When it becomes clear that Kiem Sun plans to continue his experiments, MacLeod destroys the remaining sample of the drug.

A beautiful young woman, Felicia Martins, throws herself to her death, only to revive with the realization that she is an Immortal. She seeks out Duncan MacLeod as her mentor, and becomes amorously involved with Richie Ryan. But there is much more to this "ing�nue" than meets the eye. She is in fact a long-time Immortal, engaged in a wily scheme to trap MacLeod and acquire his Quickening. MacLeod must see through her subterfuge in time to protect not only himself, but also Richie.

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.

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.