Edward Mars was a United States Marshal who sought to apprehend the fugitive Kate Austen. Their years-long game of cat-and-mouse came to an end when Mars arrested Kate in Australia. He was escorting her on Oceanic Flight 815 to Los Angeles when the plane crashed on the Island. Mars survived three days in excruciating pain, until Sawyer attempted to end his suffering by shooting him in the heart. Sawyer missed the heart and only perforated Mars' lung. Jack then euthanized Mars.
Before the crash
Edward Mars arrested Kate for the murder of her biological father, Wayne, in a bus station while she attempted to flee to Tallahassee. While he transported her by car to her arraignment in Iowa, a black horse caused him to veer off the road, allowing Kate to escape from Mars' custody, and making recapturing her a very personal matter to Mars. ("What Kate Did")
He knew that Kate felt guilty about her mother, so he set up a 24-hour stakeout around Diane for when Kate would inevitably show up. Cassidy revealed the extent of the stakeout when she dressed up to look like she was Kate posing as a Bible saleswoman and was tackled by several agents at Diane's front door. Although two agents were sitting in the diner where Diane worked, Cassidy helped Kate by spilling food on her mother so she would find Kate in the restroom away from the agents. ("Left Behind")
In the months that followed, Kate began a pattern of calling Mars on religious holidays. After she tried to visit her dying mother, the police were called to the hospital to arrest Kate, who was on the run. Kate left behind her plane, which was an item shared with her childhood sweetheart Tom Brennan, who was killed during Kate's escape from the hospital's parking lot. ("Born to Run")
After marrying Kevin Callis, Kate called Mars again to tell him she didn't want to run anymore. Sensing that Kate had fallen in love, Mars offered to stop chasing her if she could really settle down. But fearing Kevin, a police officer, would eventually discover her identity, Kate fled her husband and the chase continued. ("I Do")
Mars at last caught up with Kate in Australia, arresting her and arranging to bring her to the United States to stand trial. Mars was seated in seat 27G on Flight 815 next to Kate, whom he was escorting. He carried a Halliburton suitcase with four guns and ammo in it, and had a fifth gun in an ankle holster. During the turbulence that caused the crash, Mars was hit on the head by falling luggage, knocking him out and causing his head to bleed. While he was unconscious, Kate took his keys to remove her handcuffs, and then placed the oxygen mask on his face. ("Pilot, Part 2") ("Tabula Rasa") ("Exodus, Part 1")
On the Island: Days 1-3 (Season 1)
He was severely injured in the crash by being impaled by a piece of metal. Sawyer assumed he was dead, and took his badge and pistol. Jack attempted to keep him alive as long as possible, hoping to get him to a hospital when they were rescued, as that was his only chance to survive. On the first night Jack tended him, while Kate worried; she told Jack she was sitting next to him on the plane. ("Pilot, Part 1")
The next day, Rose asked Jack to look at him. Later Hurley helped Jack tend to him. Jack asked Hurley to hold Mars down while he removed the piece of metal, but Hurley fainted. As Jack stitched up the wound, the pain caused Mars to regain consciousness, and he snarled, "Where is she?" ("Pilot, Part 2")
When Mars regained consciousness, he told Jack that "She (Kate) is dangerous. Don't let her get to you. She is not to be trusted. She would do anything to get away." When Kate went into the tent to check on him, he attempted to strangle her. His suffering was obvious to the other survivors, some of whom questioned the use of medical supplies on an evidently terminal patient. Jack refused to let him die or to put him out of his misery. Apparently at Kate's request, Sawyer attempted to end his suffering by shooting him, but missed his heart and perforated his lung, putting him in more pain. Jack then euthanized him. ("Tabula Rasa")
On Oceanic Flight 815, Edward sat next to Kate. He did not allow her to use a knife and fork when she ate food. Shortly after escorting her to the toilet and back, Sawyer nudged his arm while walking past his seat. ("LA X, Part 1")
Once Flight 815 landed, Mars took Kate to the bathroom, where she attempted to release herself from her cuffs by using a pen she stole from Jack on the plane. After seeing part of the pen on the bathroom floor, Mars got suspicious, making Kate nervous and ending in her knocking him out. Almost immediately, Mars and the airport security started chasing Kate, though she successfully escaped by entering a taxi cab occupied by fellow Oceanic 815 passenger Claire. ("LA X, Part 2") ("What Kate Does")
- Mars has appeared in 12 episodes, his three final appearances were made by his flash-sideways counterpart.
- Although Edward Mars' name had been known from Oceanic-air.com for some time, his name was not mentioned on-screen until "I Do", when he answered a phone as "Agent Mars", and Kate called him "Edward". Until this he had been credited on the show as "The Marshal".
- Mars has appeared in flashbacks in five episodes since his death on the Island and only two before.
- Edward Mars is seen to have a wedding band.
- Eddie Mars is a character in the book The Big Sleep, who runs a casino.
- ABC frequently credits him as "the Marshall" in press releases. This is a misspelling of his occupation, which has only one "l".
- On 5 April, 1950, the Marshall Mars was lost near Hawaii when an engine fire consumed the airplane after her crew had evacuated.
- Edward Mars was the first recurring guest star to die, in his third episode.
- Witnesses of death: Jack, Sawyer, Kate
- Last words: "So, are you going to do it, or what?"