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.

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.

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 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.

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 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.

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.

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.

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.