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.