In 1996, Desmond is passed out on the floor of the bathroom, and the sink is overflowing. He gets up and sees that his 1996 nose is not bleeding.
And now he's knocking on Penny's door. (Her address? 423 Cheyne Walk.) Penny opens the door and is shocked to see him. He tells her that he came because she disconnected her phone. She tells him to grab a clue and recognize that she doesn't want to have anything to do with him. Before she can close the door, he tells her that he just needs her new phone number. Penny: "Why would I give you that?" He tries to tell her he's sorry for breaking up with her, and that is just what she doesn't want to hear. But he gets very earnest and tells her that he knows he can't undo things, but that he really needs her to listen to him. She lets him in.
She tells him to speak his piece and leave. He tells her that in eight years, he's going to need to call her. She's confused, and he starts pleading again. She wonders what's to stop him from calling her whenever he feels like it, and he promises not to call for eight years -- not until December 24, 2004. Near tears, she asks him if he'll leave once she gives him the number. He agrees, and she tells him the number. (It's 7946 0893.) He recites it, and she can't believe he's not writing it down. He tells her it wouldn't matter, and then tells her not to change the number, ever. She's had enough, and shoves him out of the apartment.
Back on the boat, Desmond wakes up. Sayid asks him for the number, and Desmond gives the number to Sayid. Sayid dials one of those handsets that the telephone repair person uses; he warns Desmond that he doesn't know how long the battery will last. The phone starts ringing. We see 1996 Desmond walk away from Penny's house. Does this mean future Desmond is catatonic? 1996 Desmond turns back and sees Penny crying in an upstairs window as she draws the curtains. And then on the boat, Desmond hears Penny answer the phone. She sounds overjoyed to hear his voice. We see 1996 Desmond, and the small smile on his face tells us he can somehow sense that something has gone right. Penny's in her house, standing in front of a Christmas tree. She asks him where he is, and he tells her that he's on a boat and that he's been on an island. Sayid looks interested, because that last line makes it seem as though Desmond has regained his memory of the recent past. Penny tells Desmond that she's been looking for him for the past three years. Which is interesting, and perhaps throws some doubt on the date we saw on the calendar. She tells him that she knows about the island, and that she's been researching...something, we don't hear what, because the line goes all staticky. We do hear her mention speaking with Charlie, which was the moment she knew Desmond was still alive. There's some more static, and a weeping Desmond tells Penny that he loves her and that he's always loved her. She tells him that she loves him, too. We get a set of intercut lines in which they each promise to find each other, no matter what. And then the phone goes dead. Sayid apologizes for not being able to keep the call going longer, but Desmond tells him he got what he needed. That was a lovely scene, with fantastic work from both actors.