Devon Marek was the first born son of the Duke of Willoughby. He was sent to Scotland in order to manage the ducal estates there. He was a spoiled aristocrat, arrogant and entitled, and thought rules did not apply to him. When he discovered a poacher on the estate, he made a game of it, and decided to hunt poachers, but in the scramble, the desperate man stabbed him to death.
Duncan MacLeod was on hand for the dying Duke's son. When Marek revived as an Immortal, MacLeod attempted to explain what he now was and the rules. Marek arrogantly insisted there were no rules that applied to him. MacLeod explained he was dead to the world, and had to start over, but Marek simply killed the man who had stabbed him, and then challenged Duncan. Duncan killed him but could not take his head because they were surprised by two soldiers. Since the soldiers had seen his body, Marek was now officially dead, and was bereft his inheritance. His death was recorded by Watcher Andrew Murray MacLeod.
In 1733, Marek met Peter Kanis, hunted him for fun, and killed him, possibly in Saxony. When he realized that Kanis was another Immortal, he kept him as a student. The passion for hunting colored Kanis' personality from then.
By 1998, Marek had managed to create a business empire. He was CEO of Keram Enterprises, a French toy company. In August, he decided the time for his revenge had come. He sent the lovely Margo to MacLeod, to lure him into his office building where he had professional killers waiting. One of Marek's employees, Lawrence Dicente, a.k.a Dice, a computer expert, recorded everything from MacLeod's arrival to the killers' hunt for him through the building.
Marek told Dice that it was all a game simulation. Dice did not know at the time that everything he saw was real. MacLeod later convinced him otherwise. In the end, things did not go quite according to plan. MacLeod escaped the trap and challenged Merek. The two fought and MacLeod beheaded Marek.