Captain von Trapp (Christopher Plummer)’s Timeline and Summary

When the film opens, Captain von Trapp doesn't seem like the most relatable guy—he's a little scary, even. He doesn't seem to be particularly kind to anyone, including his children.
He's sent a request to the abbey for a governess for his children.
When Maria arrives, he orders her to treat the kids sternly just like he does.
He leaves for an extended trip to Vienna to visit his girlfriend, Baroness Schraeder.
He comes home to find the kids enjoying themselves, and gets into an argument with Maria for letting them have fun. In a fit of anger, he fires her.
He hears the children singing a song Maria taught them and he's magically transformed into a loving father who can now allow music and happiness back into his home.
He and the baroness get engaged, but he has some lovely moments with Maria that make the baroness suspicious.
The baroness sees the captain's feelings for Maria deepen, and she tells him what he should already know.
Soon after that whole revelation, the Captain and Maria realize they're in love and get married.
Unfortunately, they don't get much of a chance to enjoy their wedded bliss, since they come home from their honeymoon to find that the Nazis have invaded Austria. Captain von Trapp has been commanded to join their navy.
Captain Von T would sooner risk life and limb than do that, so the family makes a daring escape through the Alps to get to Switzerland.