Highlander: The Series (1992)

S1E15 For Tomorrow We Die

MacLeod discovers the trail of an Immortal named Xavier St. Cloud, a man who has thrived through the ages by brutally robbing and murdering the innocent. During World War One, MacLeod narrowly avoided becoming one of Xavier's victims when he used poison gas to steal from a payroll truck. Now, in modern-day Paris, Xavier employs even more lethal gas, and MacLeod must find him before he strikes again. Although MacLeod ultimately defeats Xavier, the sinister Immortal escapes with his head. Meanwhile, Richie becomes infatuated with a glamorous older woman, unaware of her marriage, prompting Tessa to step in and help him break free.