The Samurai (S03E01)

After witnessing her husband, wealthy industrialist Michael Kent, murder her lover, Midori Koto kills Kent and seeks refuge with MacLeod. She invokes a pledge of protection made by MacLeod’s "ancestor"—who is actually MacLeod himself—over two centuries ago. Flashbacks reveal MacLeod’s shipwreck in Japan, where he helps the samurai Hideo Koto, risking his life despite the death penalty for aiding a foreigner. When Hideo is forced into ritual suicide by his lord for this act, MacLeod stands by him and promises to safeguard the Koto family, receiving Hideo’s dragon head katana. In the present, MacLeod learns that Kent is an Immortal and still alive. To avoid bringing shame to her family, Midori decides to return to Kent. Kent then challenges MacLeod, who honors his vow and liberates Midori from her unfulfilling marriage.