The grandchildren see their grandparents as endearing people and are not able to imagine them in their youth, when the grandparents were the same age. Therefore, they do not know that many grandparents have impressive abilities, the result of a life full of adventures.
This is what happens in this film, where the grandson tells his grandfather that they have kidnapped his girlfriend. Grandpa sees that the grandson is very much in love, so he decides to help him.
For this he does not hesitate to gather his old team, some men who fought and especially spied together in World War II, so that we can say that his tactics are a little outdated.
The grandson can not believe that his grandfather and his friends were a kind of spies or special forces, but that now gives him a little bit the same, because what he wants is to recover his girlfriend at all costs.