What McClane doesn't realise is that his son is now a CIA agent and involved in a high-level and extremely important mission to bring down a dangerous Russian politician.
Jack has to try to reach a man who has information that will stop the politician from taking supreme power.
But the evil Chagarin (Sergei Kolesnikov) has other ideas and wants Komarov (Sebastian Koch) to himself.
So Jack must take his father along for the ride on a high-speed mission.
It is only when the McClanes and the Russians reach Chernobyl that it emerges what the ultimate prize is.
It will be interesting to see if the young McClane is being groomed to take over the old man's mantle as all-action hero in future Die Hard adventures.