Template:Infobox Lost Character-1 Desmond David Hume is a fictional character on the ABC television series Lost portrayed by Henry Ian Cusick. Desmond was not a passenger of Flight 815. He had been stranded on the island 3 years prior to the crash as the result of a shipwreck.

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Desmond did not graduate from university, as he tells Charles Widmore because he had to support his three brothers after his father left them. The cause of the elder Hume's departure remains unknown. Desmond also served as a set designer for the Royal Shakespeare Company. He dated Penelope "Penny" Widmore for two years prior to meeting her father, who was apparently unaware of their relationship. He later comes to the conclusion that Penny is too good to be with him, so he breaks up with her.

Presumably to prove himself to Mr. Widmore, Desmond joined the Royal Scots Regiment of the British Army and became dishonorably discharged for refusing to follow orders. He served a prison sentence. Among the few possessions Desmond had returned to him upon his release was the book Our Mutual Friend by Charles Dickens. When asked by the guard releasing him why he did not take it with him to prison, he replied that he intends it to be the last thing he ever reads. Charles Widmore approaches him and reveals that he intercepted and hid every letter Desmond wrote to Penny from prison. Thinking that he has forgotten her, Penny becomes engaged to another man. Charles bribes/threatens Desmond to stay away from his daughter.

Desmond travels to America to compete in a race around the world, hoping to win it to regain his honor and anger Charles, who is hosting the event. Desmond needs a boat for the race, which he gets from Libby, whom he meets in a coffee shop soon after arriving in America. She acquired the boat when her husband David died, and believes that Desmond was meant to have it.

Before training one night in a stadium, Desmond is approached by Penny, who has tracked him down. She asks why he never wrote, but instead of explaining himself, Desmond tells her to wait one year for him (when the race will be over). While running the steps in the stadium, Desmond meets Jack, who is also running. The two have a brief but meaningful conversation where Jack explains about a patient that he cannot "fix". Desmond tells him to believe in miracles, and then talks about his training for the race. He finishes by saying "See you in another life, brother."

Later, during the race, Desmond's boat, Elizabeth, is caught in a fierce storm and he is knocked unconscious.

Desmond washes ashore on the island without his boat. A man named Kelvin Joe Inman (played by Clancy Brown) emerged from the jungle in a HAZMAT suit and takes him back to the hatch. He asks if Desmond is "him" and is upset when he realizes that he is not. Desmond watches as Kelvin inputs the numbers into a computer. When Desmond asked, "What was all that about?" Kelvin responded, "Just saving the world." He tells Desmond to inoculate himself with an unnamed vaccine every nine days, since he was out in the "quarantined" island for so long, and may be infected.

Kelvin trains Desmond about the operations of the hatch, including the button (which he explains safely discharges an unusually strong magnetic fluctuation situated beneath them) and ways to trigger a lockdown. Desmond also witnesses Kelvin painting the blacklight picture on the bulkhead doors, which was started by Kelvin's old partner, Radzinsky. Desmond asks what happened to him. Kelvin points to a stain on the ceiling, explaining it is all that is left of Radzinsky, as this is the spot where he took his own life.

Three years pass, and Desmond desperately wants to go above ground, but Kelvin never allows it, although he himself leaves for hours each day in his HAZMAT suit.

Desmond catches Kelvin drunk one night in a secret crawlspace below the floor, dangling a key above a fail-safe mechanism. Kelvin explains that if the fail-safe mechanism is activated, the hatch will be destroyed, destroying the electromagnetic fluctuation beneath them.

When Kelvin leaves one day, Desmond notices that Kelvin's HAZMAT suit has a tear on its leg. He follows Kelvin above ground, where he discovers Kelvin removing the suit and finds the air is safe to breathe. Desmond follows him to a cove, where he sees his sailboat in perfect shape. Kelvin had been leaving the hatch to fix the boat a little each day, planning to escape the island and leave Desmond behind. Kelvin startles Desmond and tells him that he knew he was being followed, and then invites Desmond to escape with him, but Desmond is worried about the button. After Kelvin expresses his doubts about the validity of the button, Desmond becomes enraged that he may have spent three years of his life on the island unnecessarily and attacks Kelvin. They struggle, and Desmond accidentally smashes Kelvin's head on a rock, killing him. Desmond then takes the key for the fail-safe mechanism from around Kelvin's neck. After, Desmond races back to the hatch, where the timer has recently reached zero and the computer is registering a system failure. A massive magnetic field builds up, attracting all metal objects to the sealed door inside the hatch, including Oceanic Flight 815, which he discovers later. Desmond manages to stop it by inputting the code, which turns off the magnetic field. However, the plane has crashed onto the island.

For forty-one days, Desmond lingers in the hatch. He gradually fell into a deep depression to the point of even contemplating his own suicide. As he opens up Our Mutual Friend, being the last book he will ever read, he finds a note that Penny had hidden inside, telling him not to despair, as well as reminding him that she will always wait for him and that she loves him. Even more depressed now, he goes into a rage and makes a mess out of the hatch. As he collapses, Desmond then hears someone shouting from the top of the hatch. Unknown to Desmond, it is Locke asking the hatch for help after Boone's fatal plane injury. When Desmond turns on a light to see who it is, Locke, thinking his prayers have been answered, quiets down. Desmond, similarly, considers the voice to be a sign that he is no longer alone, and regains hope.

When the survivors enter the hatch in "Man of Science, Man of Faith" and "Adrift," they accidentally break the computer after a brief firefight with a panicked Desmond. Convinced that the world is going to end, Desmond frantically flees the hatch in "Orientation." Jack catches up with him; Desmond tells him the code, and to enter it every 108 minutes. He begins to recognize Jack from their encounter at the stadium, and he asks him about the patient he had mentioned operating on. Desmond leaves saying, "See you in another life, yeah?" as he had in their first encounter. Although it was not shown exactly how, Desmond manages his way back to the Elizabeth and attempts to sail to Fiji. However, his plans go awry.

A drunken Desmond returns in his boat in "Live Together, Die Alone," having been unable to navigate away from the island, making him compare it and its waters to "a bloody snow globe." Later he is confronted by Locke who tells him of the station 5 (The Pearl) orientation film he and Eko saw, and Desmond begins to lose his faith in the button. While Desmond wavers back and forth with his conviction on the button, he and Locke trigger another lockdown, trapping Eko outside the computer room, and they wait for the countdown to hit zero, to see what will happen. Eko uses dynamite from the Black Rock to attempt to get back into the computer room, but he fails.

As the countdown reaches zero, Locke shows the printout he obtained from The Pearl. Desmond realizes that the date of the prior "system failure" was the same day as the plane crash, September 22, 2004. Desmond believes that his failure to push the button that day resulted in a magnetic field that pulled down Oceanic Flight 815. He is insistent that the button must be pressed, but Locke angrily reacts by destroying the computer. Desmond retrieves the key to the fail-safe mechanism, wanting to save Locke because Locke saved him the night he shouted at the hatch door. As Desmond uses the key, a giant white light envelops his face.

Immediately after turning the fail-safe key, Desmond finds himself back in time at a point when he was living with Penny Widmore. Disoriented, he doesn't, at first, remember the island. When he runs into Charlie it all comes back. Along the way to correcting his past mistakes, he meets an older woman, Mrs. Hawking (played by Fionnuala Flanagan) who tells him that his fate is to be on the island and that the universe always finds a way to fulfill fate one way or another. Teetering between accepting this and making his own fate, he gets whacked in the head and wakes up back on the Island after the implosion of the Hatch, naked and disoriented. ("Flashes Before Your Eyes")

Eventually, he meets Hurley, who gives him some clothes to wear, and escorts him back to the beach camp. En route, Desmond displays some evidence of precognition or déjà vu, talking about a "speech" that Locke has yet to give. When Hurley questions him about it, Desmond back-pedals, seeming to recognize both the phenomenon and the necessity of hiding it; but after the speech Hurley realizes that Desmond had foreknowledge of it.

This precognitive ability is continued in "Every Man for Himself," in which he apparently foresees lightning striking Claire's tent. He borrows a golf club from Paulo in order to construct a lightning rod, which later diverts the bolt.

In the episode "The Cost of Living," Desmond tells Sayid that he thinks the computer in the Swan was also used to communicate with other hatches on the island. He and Locke have come up with a plan to go to the Pearl station and try to use the computer in there to communicate with the Others in attempts to rescue Jack, Kate, and Sawyer. Sayid joins Locke and Desmond and, along with Nikki and Paulo, venture to the Pearl. While there, Desmond and the others witness Mr. Eko's death. Desmond and the group bury Eko in "I Do."

In the next episode ("Flashes Before Your Eyes"), Locke asks Desmond to find Charlie and Hurley and meet him and Sayid in the jungle, where he proceeds to tell them about Eko's death. As he is doing so, Desmond falls into a trance, and then immediately takes off. Locke, Charlie, Sayid and Hurley follow him back to the beach, where he strips and dives into the sea. They soon notice that he is swimming towards a body in the open sea, which turns out to be Claire. Desmond rescues and resuscitates her. Charlie repeatadly asks how he knew she was drowning, but Desmond offers no answer. Hurley comes to the conclusion that Desmond "sees the future". Later, Charlie and Hurley conspire to get Desmond drunk. After a struggle, Desmond tells Charlie he has been seeing bits of the future, mostly of events where Charlie dies. Charlie was supposed to drown saving Claire. He was also supposed to die when lightning struck Claire's tent. However, he says, the Universe has a way of "course-correcting" - implying that he cannot stave off Charlie's death forever.

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In keeping with the show's habit of naming important characters after important philosophers whose philosophies are broadly consistent with their namesake characters (e.g., John Locke and Jean-Jacques Rousseau), Desmond David Hume is named after the famous Scottish Enlightenment philosopher, economist, and historian David Hume.

• In 2006, Henry Ian Cusick was nominated for an Emmy award for his portrayal of Desmond in the season two finale.
• Desmond began as a recurring character in season two, appearing in four episodes (including the season finale of season two in which he was the main focus of the episode) and was added to the main cast in season three.
• Henry Ian Cusick took the role because it allowed him to use his real accent.
• Desmond has the habit of calling others around him "brother."
• Desmond is the second and currently only main character to explicitly show any paranormal and supernatural behaviour (Walt exhibited such behaviour on a few occasions during the first season).