Luke has just returned from purchasing several new droids from the Jawas. Along with everything else he has to do on Tatooine, with his uncle, he hated every minute of it. They tried to sell Luke and Uncle Owen a defective unit, of course. Thankfully the protocol droid pointed out a useful alternative right away, and there still doesn't seem much of a problem with that one. Until, that is, it plays the loop of the kidnapped princess and refuses the play the whole thing, and then wanders off and...Well, thank goodness the protocol droid is functioning smoothly. Oddly eccentric, but not causing any problems. More useful than most.
As Luke takes...what was its name, C-3PO?...along with him, he's already forgetting the protocol droid was ever significant at all. Now it's just becoming irritating, and this will probably not change except for the worse. A migraine. Luke's getting a migraine. He doesn't know which of the units to blame.
Soon, improbably, Luke's ended up at the doorstep of Old Ben, where he's spent almost as many hours as the ones with his friends and probably more than the ones he's logged in on the moisture farm. He's not guilty about that at all. Old Ben turns out to be the Obi-Wan the kidnapped princess was addressing in her loop. He may not be the crazy old hermit he seems after all! Life is full of surprises.
Luke's aged friend is telling him once again about his birth father, the one Uncle Owen constantly dismisses and belittles, the one Luke never met. Old Ben, or whoever he is, says Luke's father was betrayed and...murdered by the Imperial military figure Darth Vader. Luke looks around bewilderedly. He's putting that protocol droid back together after it was busted up in the Sand People attack they narrowly escaped thanks to Old Ben.
Now they're rushing off. Luke's realizing that things are going to be changing rapidly. He's becoming lost in his own dreams, which are suddenly becoming reality! The last thing he cares about is whatever the protocol droid is babbling. That's become routine at this point.
But Threepio has something important to say, something Luke really ought to hear:
"My construction took so long, even my own mother forgot what was happening. My body was destroyed, and I was remade. I was reshaped in the form of a droid I'd once made myself. That's probably why my mother became so confused. I'm afraid this is all too easy to understand. The story of our lives can seem like it's one thing for the longest time, and when it changes, it can be hard to accept that things aren't the same anymore. I don't know who this Vader person is, but I hope you're not planning to go after him. Master Luke, I am your father. Do you hear me? Oh dear. Here we go again!"