Simon Escher (Garret Dillahunt) was the ace professional assassin/operative for Management prior to Michael Westen being "burned." He is responsible for numerous bombings, arsons, kidnappings and assassinations for the organization and apparently was high-ranking enough to gain access to the names and occupations of all members of Management. Sometime prior to Season 3, he went insane and began carrying out terrorist attacks for his own interests. According to "Vaughn", his handler, Simon became too high-risk for Management to continue doing business with and so they attempted to have him killed; an effort that failed, and led to Simon beginning his vendetta against Management.
He compiled a list of names, aliases, occupations and locations of all members of Management as an insurance policy. He used a book-code, the Escher Family Bible, to encrypt "The List" which can only be decrypted by a second portion of the code. Realizing he was too small a cog in the machine to strike at Management, he enlisted the help of a private-sector corporation called Drake Technologies, and its CEO, John Barrett, who he promised the list to in exchange for assisting him in taking Management out. Sometime after, however, he was captured by Management and taken into exile as a super-max prisoner. Management then turned their sights to another skilled and talented spy - Michael Westen - and had him burned and all of Simon's crimes pinned on him to secure his dismissal. Somehow this information was discovered by Simon, who became obsessed with/furious at Michael for taking the "credit for his work."
Barrett, desperate to obtain the NOC List, enlisted the services of a "Freelance Psychopath" named Mason Gilroy and his associates to have Simon broken out of a super-max prison transport airplane so he could lead them to the Family Bible. Barret paid $10-million dollars to intercept a flight meant to transport Simon from Chile to Poland. After Michael gunned down Strickler, a professional assassin, Mason Gilroy, took it upon himself to break Simon out for the price-tag promised to them, ultimately forcing Michael to assist him in the dangerous jail-break, even though Simon requested Micheals involvement to begin with. Once the pilots of the plane were bribed by Gilroy to release Simon, he turned on Gilroy: shooting him in the abdomen and strapping him to an explosive device that blew him up inside of his car.
Now a free man and on the loose once again, Simon first turned his attention to Michael, whom he needed to lure Management to a trap in Miami, using a bomb in the basement of the Epoc Hotel as oeverage. After a game of cat-and-mouse between them, Michael ultimately contacted "The Old Man" - a high-ranking member of Management that Michael had met after Carla's death - and informed Management of Simon's plan to capture/kill him. Their meeting atop a helipad turned deadly, however, when Simon detonated a bomb that blew up the helicopter, knowing all along that Micheal never intended to sacrifice Managment. After the explosion, Simon infiltrated the helipad under the disguise of a security officer and revealed he knew how it would all go down from the begining. He killed several bodyguards working for The Old Man until he was able to capture him and beat up Michael, with the latter barely escaping death by sliding down a construction chute. Simon restrained The Old Man inside the back of an ambulance that served as his escape vehicle and then fled the scene of the bombings. Michael hijacked a utility truck and crashed it into the side of the ambulance as Simon was fleeing. A brief struggle between Simon and Michael ended with Simon facing the business end of his own Walther P99. Micheal was going to kill Simon, but Management intervened and told him not to, as it would ruin his future. Simon, instigating Micheal to ignore Management and pull the trigger claimed "Oh, he owns you now boy." Promising Michael that he'd soon "end up just like me."
Once again a prisoner of Management, Simon resurfaced towards the middle of Season 4, when Michael requested he be returned to Miami for interrogation about who he was working for. Simon broke free of his restraints and attacked Michael, hurling them both out of a window and onto a deck. There, he told Michael of the location of a buried stash he had hidden inside a cemetery containing an audio-tape that implicated "Vaughn" in Michael's burn notice. He also led Michael and his allies to John Barrett. also he was mentioned in season 5 where michael had Simon moved to the same prison as Vaughn. About "[going on] two years" before his reappearance in season 7 the CIA had put Simon back to work, like Michael, and had him run jobs for them where there was neeed for someone to get his hands dirty. His recent CIA work is described by Strong as, "...[he is] a top-notch operator, no one has a better record in high risk situations."When Michael is meeting with James and Sonia in Latin America , Strong, Michael's CIA handler sets up an extraction for James and needed an off the books teams of mercenarys. Strong hires Simon to lead Alpha team of the extraction operarion. When Simon's team is killed assaulting "the east boathouse" after the failed ambush on James' convoy, along with almost all of James' team, that just left Simon, Micheal, and one of James' men, who Micheal knocked out. Much to Micheal's dismay and shock, Simon reveals himself to Michael as "Alpha team" while executing one of James' men wounded in the firefight. Michael Debates shooting Simon but reluctantly doesn't when Simon explains that Strong needed someone who Michael would never work with so as not to blow his cover. Simon and Michael plan to set up an ambush for James, who Micheal convinced to come to his rescue over their radios. During Micheal's conversation with James, Simon began to torture one of James' wounded and restrained men, to "make it convincing." His (ruthless and murderous) and Michael's (non lethal and non invasive) capture methods clash and they begin to fight after Simon executes the same one of James' men he was torturing earlier. The fight begins with them each having a pistol, but are both disarmed by each other. During hand-to-hand combat, Michael starts to subdue Simon, who pulls a knife and manages to cut Micheal's arm and break free. Simon, now bleeding from his mouth, nose, and from various cuts on his face begins to bargin when it becomes clear Micheal has the upper hand. With both of them fighting for control of the knife, Micheal again gains the advantage to pushes it slowly into Simon's chest, almost certainly killing him. The, presumably, last scene of Simon shows him on the floor of the boathouse when Sam, Jessie, and Strong enter the boathouse, not moving on his back, with the knife still embeded in his chest.