Desmond Hume ( Henry Ian Cusick) is one of the pivotal characters in "Lost". He is a Scotsman who is madly in love with Penelope Widmore (Sonya Walger), the daughter of Charles Widmore (Alan Dale), a wealthy business tycoon. Mr. Widmore does not approve of Desmond, and that disapproval causes Desmond great insecurity. He and Penelope break up, and Desmond enters a boat race around the world to prove to Mr. Widmore that he is worthy of Penny's love.
Desmond has a rather eventful past. He spent time in the Scottish armed services and at one point joined a monastery looking for the meaning of his life. He meets Penny just as he is about to leave the brotherhood forever.
Desmond is given a sailboat by a woman he just met, named Libby (Cynthia Watros), and he sets off on his quest to prove himself. He encounters a storm, and wrecks on a mysterious island, where he meets a man asking if Desmond is his replacement. Desmond does not understand what the man is talking about, but quickly learns that he will be the keeper of a hatch buried on the island, where he must punch in a series of numbers every 108 minutes. If he fails to do so, then the world will end. Desmond spends several years on the island, alone in the hatch. Ultimately, it is his failure to punch in the numbers that leads to the crash of Oceanic Flight 815. There is a huge magnetic force field on the island, and punching in the numbers keeps this field at bay.
The hatch is eventually blown up, and Desmond becomes a member of the group of survivors on the island. He forms a friendship with Charlie (Dominic Monaghan), and begins to have very bad dreams depicting Charlie's death. He does everything he can to warn Charlie and save him, but in the end realizes that Charlie's death is destined to happen.
The passengers become aware of a boat offshore, and plan to contact it with hopes of rescue. They think that Penny has sent the boat looking for Desmond, and that they will all be saved. Just before he dies, Charlie relays the message to Desmond that the boat does not belong to Penny. Desmond then realizes that the boat most likely belongs to Charles Widmore, who once lived on the island as an "Other". Desmond then realizes the danger that the island inhabitants face.
Everything that Desmond does is because of his love for Penny and his hope of being reunited with her. A memorable scene occurs when she and Desmond speak by phone, and Penny realizes he is alive. Thanks to events leading up to the rescue of some of the passengers, Desmond and Penny find each other again, go on to marry, and have a son named Charlie.
"I won't call for eight years. December 24, 2004, Christmas Eve. I promise. Please, Pen."
"You're gonna die, Charlie."
"I've got to go, and you've got to get as far away from here as possible."