It's the year 2024 and all the ozone above the Earth has gone. To protect people from dying, MacLeod helped in the construction of a giant "shield", several years ago. But, since there isn't an Immortal left after MacLeod's victory in the previous film, he has stopped being an Immortal himself.
Now he is just an old man until MacLeod's old nemesis from the past (General Katana) travels into the future to kill Connor once an for all. It turns out that MacLeod was banished from a distant past with his mentor Ramirez, who he calls upon to help him defeat Katana, before Katana kills him. MacLeod is also aided by Louise Marcus, an environmental activist that believes the ozone layer as repaired itself and "the shield" is no longer necessary.