Agent Donald "Don" Self was an agent of the Department of Homeland Security. In season 4 he worked with The Scylla Team for his own purposes.
First appearing in the fourth season premiere, he represents himself as a Homeland Security agent who gives Lincoln Burrows and Michael Scofield the mission of bringing down the company and finding "Scylla", a key card that stores a wealth of information about "The Company." However, he eventually betrays them, taking Scylla without holding up his end of the bargain, granting freedom to the team. He instead wanted to find a 'buyer' for Scylla, an apparently private interest. Not much is known about him but he is stated as a hardworking Homeland Security Agent who tries to bring down The Company but has yet to be successful. He has worked for five years to bring down The Company and has worked with James Whistler and Aldo Burrows (Michael and Lincoln's father), the latter has also tried to locate Scylla. According to a background check made on the character by The Company in the episode "Five the Hard Way", Self studied law on Long Island, before spending the next 18 years moving around DOD and DOJ. He began working for Homeland Security in 2002. Agent Self later told Mahone that he had a wife that died while giving - his unborn infant died too. A picture of his wife is seen at his desk several times and he once played a message of her voice at his answering machine. This was later revealed to be a lie, as Self's wife was living in a New York hospital. The General had her murdered for Self's failures. Self first appeared when Michael and Lincoln were arrested and were in his custody. He negotiated a deal with the pair to take down The Company. Self says that they can either track down The Company and all charges will be dropped or they can refuse do it and go to prison. At first they refuse, but when a Company operative named Wyatt tries to kill them Michael contacts Self and informs him that they agree to the operation. As Sucre, Mahone, Bellick, Sara, and Roland Glenn, a computer hijacker, come along with them, Self points out that if they do it there is no coming back and that he is their boss. Under pressure from his boss, who wants to cancel the mission, Self tells Scofield that he has 24 hours to locate the second Scylla card or the team will go back to prison. When the mission is terminated, Self chases the team down, arresting all of them except Scofield, who escapes and watches a meeting between the six card-holders. After taking a picture of all the card-holders, Scofield confronts Self and shows him the picture, and Self agrees to let them find the rest of the Scylla cards. Later, Self helps the team by luring someone out of their office for lunch, leaving the team to get to a safe which contains a Scylla card. When General Jonathan Krantz, the leader of the Company, discovers Self had images of him enhanced, Wyatt confronts Self and tells him that the General "likes his privacy." Taking Mahone's advice; to get aggressive, Self meets the General face-to-face and blackmails him, threatening to reveal to the public missions he was involved in, thus making it harder for the Company to remain covert. In Episode 12, "Selfless," Self apparently works with the team as they finally recover the Scylla key card, but he ultimately betrays them by killing a federal agent and keeping the recovered Scylla key card for himself, ostensibly to sell to a private bidder. However in Episode 13, "Deal or No Deal", Self finds himself with two problems; a buyer for Scylla, and the mistrust of Michael Scofield, who removed a part of the device. While his apprehension of T-Bag led to Gretchen and a buyer, he ultimately demanded the missing part of Scylla from Scofield, who suggested he "Come and get it." On the next episode,"Just Business" Self and Gretchen barges into the warehouse to get the final missing piece of Scylla. Self calls Michael and gives him one last chance to hand over the piece of Scylla peacefully or by force and Michael says,"Come and get it!" Self, then proceeds to fire smoke grenades through the windows of the warehouse. Michael, Sara, and Sucre try exiting out of the warehouse,but Self fires his M16 towards the door, trapping them. Self proceeds to continue his strategy,until Lincoln pistol whips Self across the face and drags him into the warehouse. The crew are about to take Scylla, until Gretchen, armed, points her MP5 at the crew, while Sara aims her gun at Gretchen. Self and Gretchen escape. They head into a hotel and watch the warehouse from a camera that was inside the gas canister Self fired into the warehouse. They see Michael putting the final piece of Scylla in his hiding place. The hotel clerk calls and informs Self that Sucre was asking questions about him and Self and Gretchen flee the hotel. With Gretchen already gone and Self packing his things, Lincoln fires a rocket launcher at Self's window but misses Self. Self flees his room and heads down the stairs, but sees Sucre and Gretchen fighting, so he goes the other way and uses the fire ladder to escape, although Michael has tampered with it and Self lands hard on the ground which gives Michael the opportunity to punch Self in the face and take Scylla from Self. Although, Self then catches up with a disoriented Micheal, takes Scylla back and points a gun at Michael and apologizes for doing his,but says "this is just business." Before he can shoot Michael, the company agents start firing at Self and Gretchen arrives with a van and Self hops in and they escape. They arrive at the warehouse and take the final piece of Scylla. Gretchen holds Self at gunpoint and Self assures her that she will get her sister and daughter back soon and they head to their rendezvous spot to meet the go between for the buyer, Viking. After asking Viking if the buyer of Scylla is coming, Self shoots Viking and his bodyguards and tosses their corpse into the sea. Self is next seen waiting with Gretchen for the Scylla buyer. After getting a call from Gretchen's sister, Rita, Gretchen tells Self that the company has T-Bag and unfortunately he might have told the company where they are. So before Lincoln and Sucre could track them, Self and Gretchen destroy their cell phones and flee. They're next seen at a phone store and look injured with bloody scratches on their faces. They buy a new phone and tell the store owner not to tell anyone they were there. They head to the warehouse to wait for the buyer. The buyer arrives and Self and Gretchen hold the buyer at gunpoint. Gretchen forces Self to hand Scylla to the buyer or they will be in grave danger. Self hands over Scylla and they look at the computer saying, "Power" "Bargain" and "Wind". They hear noise and Self and Gretchen go to investigate, but are betrayed by the buyer when he points his gun at them and they run for cover and a shootout occurs. The buyer shoots Self in the shoulder and flees with the money and Scylla. Later they are to work with Lincoln and T-Bag to recover Scylla. When the team fails to recover Scylla, Krantz decides to order the death of Self's wife, who was actually alive and in a persistent vegetative state due to Self's drunk and reckless behavior. Self then escapes, but gets arrested when at the hospital, where one of Christina's men injects him with a serum that gradually leaves him in the same state his wife was in. He refuses to help the police with locating Burrows and Scofield because they failed at protecting him, and is left in his vegetative state for the rest of his life.