Slan Quince was born in The United States of America in 1787, Slan Quince was the only child of a blacksmith, from whom he learned his handicraft. After his ship was sunk by the British during the War of 1812, he died and was reborn as an Immortal. He learned The Rules of The Game from The Immortal Patrick Stanze, living the first half of his life as a blacksmith, like his father. Later, he began to hunt Immortals, even making his own customized sword with a projectile hidden in the handle. Because he took pleasure in hunting not only other Immortals, but also their close friends, he began to be called "Slan the Cat" by other Immortals. During sword fights, Slan carried a metallic mask, in order to protect his face, which, according to his opinion, was his most valuable property.
In 1992, Slan was in Seacouver where he sought out Duncan MacLeod. One night, he breaks into Duncan’s antique store seeking a fight with Duncan, But to his surprise, Connor Macleod was there as well looking to kill Slan As Connor advances on Quince, police sirens begin to wail nearby, prompting Quince to break off the fight. Promising to meet The MacLeods again, Quince leaps through the front window, escaping into the street. The next day, Quince parks outside the antique store, observing Tessa's movements. However, Connor appears, making his presence known to the other Immortal, who quickly drives off like a maniac almost knocking down some people. Later, Slan manages to overpower Tessa and tie her up. Duncan arrives and sees Slan. Revealing Tessa, tied to a chair and helpless, Slan demands that Duncan drop his sword, pressing an electric saw to the side of Tessa's head. In response, Duncan slashes a nearby electrical cord, cutting power to Slan's tool. A brief fight ensues, until Slan bats Duncan away and grabs Tessa again, using her as a shield. He taunts Duncan: "Be a good boy, and I might just let her live." He lunges at Duncan again, but breaks off and runs away, leaving MacLeod to see to his terrified lover. Days later Slan calls Duncan but gets Tessa instead and tells her to tell Macleod to meet him at meet him at Soldiers' Bridge. He has also promised to come for Tessa should Duncan lose or not show. Arriving at the bridge, Connor approaches Quince, and challenges him. Quince agrees, donning his trademark mask, and the fight is on. As Duncan arrives, Quince unleashes a sneak attack, firing a dagger into Connor's heart. The elder Highlander is able to escape beheading however by diving into the river before he expires. In a rage, Duncan comes at Quince in a blinding furry. Slan then tries to Kill Duncan by charging at him only for Duncan to slash Quince across the stomach, forcing him to his knees, and then beheads him in a single swift stroke and receives his quickening.
Slan was devious and methodical, stalking his opponents for days to weeks on end before challenging them. Like most evil Immortals, he would take his prey's loved ones hostage and use them as leverage in his fights. He respected The Rules, however.
Slan used his size and strength to his advantage, overpowering and wearing down his opponents before taking the kill. He was devious enough, however, to employ sneak attacks when he felt the situation called for it. His weapon of choice was a customized two-handed broadsword with a specialized gun barrel built into the pommel. With it, he could fire a specialized dagger at his opponent.
Slan was the first Immortal to be beheaded in the series.
Unlike as in the movies his beheading couldn't been shown to the audience. Duncan simply slashes with his sword, you see Slan's headless torso while lightning comes out of his neck. Then the camera zoomed in on Slan's supposed to be beheaded corpse. From all episodes this was the most specific beheading.
Slan was born 1787 and died during the war in 1813, this means that he was 26 years old when he became Immortal. Richard Moll who portrayed Slan was 49 when he took the role.
For some reason Connor seemed to know Slan very well. Slan didn't know Connor. Many fans have inferred that Quince was send by Jacob Kell, or at least brought on Duncan's trail by him. This however has never been confirmed by the producers or director.
Slan Quince also appeared in an rather obscure German Highlander novel called "Highlander – Die Rückkehr des Unsterblichen" written by Martin Eisele. Fragments from the episode The Gathering are used as flashbacks.