Season 1

Mike works as a parking lot attendant at the courthouse. In his off-hours he engages in security and "muscle" jobs to help support Stacey and Kaylee. Jimmy frequently deals with Mike when leaving the parking lot, irritated with Mike's demands for payment or the right number of validation stickers.

Philadelphia officers involved in the investigation of two murdered cops interrogate Mike, who hires Jimmy to represent him. Mike has Jimmy create a diversion, enabling Mike to steal one detective's notepad to learn what they know. He finds that Stacey contacted them after finding money hidden in the lining of one of her suitcases. Mike admits to her that he was involved in corruption in Philadelphia, and confesses that he "broke" his son Matt by persuading him to go along. Matt's partner and another cop killed him for fear he would report them, so Mike retaliated by killing the two of them and then moved to Albuquerque to be near his daughter-in-law and granddaughter. Stacey accepts Mike's explanation and consoles him. The detectives leave for Philadelphia, and one privately assures Mike that he has little to fear. Mike aids Jimmy in proving that his clients, Betsy and Craig Kettleman, staged their own disappearance. He then helps Jimmy recover and return the money the Kettlemans embezzled.

On one of his "muscle" jobs, Mike is employed by Daniel Wormald ("Pryce") to protect him during a drug deal with Nacho Varga. Mike has no weapon, but remains calm and controlled. When the payment is $20 short, Mike insists that Nacho pay Pryce the full amount. After the deal is complete, Mike explains that he investigated Nacho beforehand and determined he was operating without the knowledge of his bosses in the Salamanca drug cartel, giving him an incentive to ensure that the transaction went smoothly.

Season 2

Impressed by Mike's work for Pryce, Nacho approaches him with a request to kill his boss Tuco Salamanca, Hector's nephew. Nacho fears Tuco may learn about his outside drug deals, and that Tuco's erratic behavior will draw unwanted police attention to the Salamanca drug business. Rather than kill Tuco, Mike engineers a public altercation so that Tuco is sentenced to prison for assault. Hector wants to reduce Tuco's prison sentence by having Mike tell police the gun Tuco was carrying was his, and threatens Stacey and Kaylee so Mike will comply. Mike agrees to take responsibility for the gun in exchange for a $50,000 payment.

Upset at Hector's threats to Kaylee and Stacey, and fearing Hector will learn the truth behind his altercation with Tuco, Mike attempts to disrupt Hector's drug trade by hijacking a Salamanca truck and stealing the $250,000 it carries, but leaving the driver, Ximenez Lecerda, tied up at the side of the road. He intended for a "Good Samaritan" to free Ximenez and contact the police, but learns from Nacho that when someone stopped to help, Ximenez called Hector, and Hector's crew cleaned up the scene and killed the Good Samaritan before police could be summoned.

Mike decides to kill Hector and procures a black market sniper rifle. As he prepares to fire, he is suddenly interrupted by the horn of his car. Mike finds a branch wedged against the horn and a note on the windshield with a single word: "don't".^[9]

Season 3

Mike finds his moves have been tracked by Gus Fring, the owner of the Los Pollos Hermanos restaurant chain, which is part of the cartel's drug trafficking chain. Gus meets with Mike and explains that he does not want Hector dead until Gus decides the time is right. He encourages Mike to continue to disrupt Hector's drug trafficking and attempts to pay him, but Mike does not accept the money. He asks for help to launder the $250,000 he stole, and Gus obliges by arranging for Madrigal Electromotive, the parent company of Los Pollos and a participant in its drug activities, to hire Mike as a contracted security expert and pay him monthly consulting fees. Mike joins Stacey at group therapy sessions to help her overcome Matt's death.

Season 4

Mike quits work at the parking lot and conducts actual security consulting at Madrigal. Lydia Rodarte-Quayle informs him the consulting contract was supposed to be a paper transaction, but Mike argues that his inspections provide plausible cover if anyone questions the payments. When Lydia complains to Gus, he tacitly approves of Mike's actions. At the group therapy sessions, Mike confronts another attendee over his lies, which causes a temporary rift between Stacey and Mike.

Tension between the Salamancas and Gus' organization leads to Hector Salamanca suffering a stroke. Gus discreetly pays for his recovery to the point where he recovers his mental faculties and can move his right index finger. Gus secretly initiates construction of a meth lab under an industrial laundry as part of a plan to end his reliance on cartel cocaine smuggled from Mexico and puts Mike in charge. Mike arranges for structural engineers to visit and assess the site while Gus silently observes. Gus selects German Werner Ziegler to oversee construction of the lab and has Mike arrange the accommodations and security for Werner and his men during the months-long project. Over the subsequent months, Mike befriends Werner and even covers for him to Gus when Werner inadvertently reveals some details of the lab's construction to patrons at a local bar. When construction falls behind schedule, a homesick Werner escapes, intending to meet his wife at a nearby spa. Mike catches up to Werner and realizes that he has inadvertently revealed the existence of a construction project to Hector's nephew Lalo Salamanca, who has arrived to take over the Salamanca drug business. Gus realizes Werner will have to be killed to protect the secret of the meth lab. He offers to send men to do it, but Mike accepts responsibility because Werner escaped on his watch, and says he will do it himself. He convinces Werner to tell his wife to return to Germany, then executes him in the desert.^[10]

Season 5

Werner's death forces Gus to halt construction of the lab. Mike reacts with disgust at Gus's seeming lack of compassion for Werner and refuses Gus' offer to continue paying him during the delay. Mike continues to struggle with Werner's death and drinks to excess. He becomes alienated from his family when he loses his temper with Kaylee, which leads Stacey to ask Mike to keep his distance.

After a night of drinking, Mike is set upon by a street gang and breaks the leader's arm before walking away. Mike is stabbed during a second altercation with the gang, which he sought out of guilt for Werner's death. He awakens at a ranch in Mexico that has ties to Gus, where his wounds have been treated by Dr. Barry Goodman. Gus asks for his aid against the Salamancas because Mike understands Gus' need for revenge. Mike secretly points police to Lalo's car and its ties to the murder of Fred the money wire clerk, which causes Lalo's arrest. Gus wants Lalo released, so Mike gives Jimmy details about the work he did to investigate to Lalo. Jimmy uses the information to accuse police of witness tampering, enabling him to win Lalo's release on bail. Mike spends time with Kaylee and tells Stacey he is over the recent events that angered him.

Lalo has Jimmy pick up the $7 million in bail money from a remote site in the desert. Several gunmen stop Jimmy, take the cash and prepare to kill him. Mike was tracking Jimmy for Gus and kills all but one of the attackers, who escapes. When Jimmy's car breaks down, Mike and Jimmy take the money and walk cross-country, camp overnight, and then resume their trek the next morning. When they see the surviving gunman is still searching, they work together to kill him. Jimmy and Mike make their way to a truck stop, where Tyrus and Victor pick them up. Jimmy posts Lalo's bail and, following Mike's orders, says he was alone and his car broke down, so he walked in order to avoid risking the money. Mike updates Gus, who realizes Juan Bolsa hired the gunmen in the belief that he was protecting Gus' business by keeping Lalo in jail.

Lalo intends to skip bail and return to Mexico. Nacho brings him to the same place where Jimmy received Lalo's bail money so that Leonel and Marco can pick him up. Instead, Lalo searches for Jimmy's car. After finding it, he returns to Albuquerque with Nacho and goes to Kim and Jimmy's apartment. Mike calls Jimmy to alert him to Lalo's imminent arrival and directs Jimmy to leave his phone on and hidden so Mike can listen in. As Mike trains a sniper rifle on Lalo from a nearby roof, Lalo reveals he found bullet holes in Jimmy's car. Kim tells Lalo that passers-by probably shot at the car for fun and berates him for not trusting Jimmy. Lalo appears satisfied and departs.

Jimmy asks Mike why he is protecting him, but Mike hangs up. Mike informs Gus that Lalo is en route to his home in Chihuahua and Nacho is with him. Gus tells Mike he sent gunmen to kill Lalo and says Nacho might be able to help. Jimmy goes to Mike's house and demands to know why Mike has been aiding him. Mike tells Jimmy that Lalo will be killed that night. Lalo kills all but one of Gus' hitmen, forces the survivor to call his contact and report Lalo's death, then walks away from his home.

Season 6

Nacho flees after opening the gate to Lalo's home so the hitmen can enter, and Tyrus later directs him to a motel. Inside his room he finds a gun, cash, and a cell phone. Nacho calls Tyrus, who tells him to hide until it is safe to move. He then attempts to call Mike, who declines to answer.^[11] While Nacho remains hidden, Mike and Gus' men enter his home and pay his girlfriends to leave town. They break into Nacho's safe, from which Mike removes the cash and the fake Canadian IDs Nacho had made for himself and his father Manuel. Victor delivers a duplicate safe, into which Mike places the cash, Nacho's fake ID, and an envelope. Nacho discovers he is being surveilled and confirms the watcher is reporting to Gus, causing him to realize Gus has betrayed him to the cartel. A cartel hit team led by the Cousins arrives and a firefight breaks out. Nacho escapes in a stolen truck. Mike engages in a standoff with Tyrus and Gus because he wants to lead a team to Mexico to find Nacho, but Gus wants to force Nacho to reveal himself by holding Manuel hostage.^[12]

Mike receives a call from Nacho, who asks to speak to Gus. Nacho offers to give himself up as long as Manuel is protected. Gus arranges to smuggle Nacho into the U.S. Afterwards, Mike and Nacho go over the plan for Nacho to absolve Gus of blame for Lalo's death by falsely blaming another drug family. After confessing, Nacho will attempt to flee so that Victor can kill him, guaranteeing his death will be swift and the Salamancas will not torture him. Mike administers a beating so it will appear Nacho was captured. While Mike watches and trains his rifle on the location, Gus, Tyrus, and Victor meet with Juan Bolsa, Hector Salamanca, and the Cousins to hand Nacho over. Nacho claims he killed Lalo while working with a rival family, the Alvarezes. He further absolves Gus by admitting he tried to kill Hector, but that Gus saved him. Rather than attempt to flee, Nacho uses a piece of broken glass from Gus' trash to free himself from his restraints, seize Juan's gun, and kill himself. As Gus and his men depart, the Cousins assist Hector to fire bullets into Nacho's lifeless body. Mike places his rifle in its carrying case and walks back to the road so Gus, Tyrus, and Victor can pick him up.^[13]

Mike has his men follow Kim and Jimmy. After Kim confronts the men surveilling her, Mike tells her the men work for him and Lalo may still be alive, and Kim realizes Mike is the man who helped Jimmy in the desert. When Kim asks why he chose to tell her rather than Jimmy about Lalo, Mike tells her she is "made of sterner stuff". Kim recognizes Mike as the former courthouse parking attendant, and she later chooses not to tell Jimmy that Lalo may still be alive.^[14] As Gus continues to worry over the possibility that Lalo is not dead, he and Mike go to the site of the planned meth lab, where Gus hides a gun on an excavator.^[15] After Lalo kills Howard Hamlin and forces Kim to drive to Gus's house and shoot him, Mike intercepts Kim, then leads the majority of his men to her apartment. Gus recognizes the shooting attempt as a diversion and drives to Lavandería Brillante, where he is ambushed by Lalo, who forces him to reveal the underground site where Gus's meth lab is being constructed. Gus kills Lalo, but is wounded himself. Mike later supervises the cleanup of Howard's murder and the staging of his death as a suicide, as well as the burial of Howard and Lalo under the floor of the meth lab. Some time later, Mike informs Manuel of Nacho's death and promises revenge on the Salamancas. Manuel dismissively tells Mike he is no better than the criminals with whom he associates.

By 2008, Mike occasionally serves as a private investigator for Saul while still working full-time for Gus. After Saul is kidnapped by Walter White and Jesse Pinkman during their effort to make Saul represent Brandon Mayhew ("Badger"), Mike does a background check on Walt. Mike's report to Saul includes the fact Walt has cancer. Mike describes Walt as an amateur and advises against working with him, but Saul is impressed by the quality of Walt's meth and decides to offer Walt his services.

Season 2

After Walt allows Jane to die from a heroin overdose, Saul dispatches Mike to clean Jesse's apartment. Mike removes all traces of the drugs and provides Jesse advice that enables him to avoid incriminating himself when speaking to police after Mike leaves. When Jesse later goes missing Mike tracks him down and drives Walt to the location.

Season 3

With Walt and Skyler White in the middle of a divorce, Saul has Mike spy on Skyler. Mike sees Walt arrive home, followed soon after by Tuco's cousins, who intend to kill Walt in retaliation for Tuco's death. Mike has Gus call off the cousins, since Walt is central to Gus's meth making scheme, and Gus convinces them to instead target Hank, the DEA agent who shot Tuco. Gus then anonymously warns Hank, who is able to fight back. He survives the attack and kills one cousin, and Mike kills the other in the hospital.

The cartel disrupts Gus' meth distribution and he has Mike investigate. Mike kills the four cartel operatives sent to harass Duane Chow, one of Gus' chemical suppliers. He later hides in one of the Los Pollos Hermanos trucks during a drug run so he can learn the cartel's tactics and implement countermeasures that protect future drug shipments.

While Walt and Jesse have been cooking meth in the underground superlab, Jesse has become more unstable. He learns that two of Gus's local drug dealers were responsible for the death of his friend Combo and Tomás, the younger brother of Jesse's girlfriend Andrea. Knowing Jesse intends to kill the dealers, Walt acts first and runs them down with his car, then tells Jesse to flee. Gus keeps Walt on, but requires that he work with Gale again. Walt correctly fears that once Gale knows enough to take over, Gus will have Walt and Jesse killed. Saul tricks Mike into looking for Jesse in the wrong place, giving Walt time to meet Jesse and tell him to find Gale's address. Mike later escorts Walt back to the lab on the pretense of responding to a chemical spill, but Walt knows Mike is supposed to kill him. Walt begs Mike not to kill him, and offers to give up Jesse in exchange for his own life. Mike allows Walt to call Jesse and find out where he is hiding. Instead, Walt tells Jesse to kill Gale so that Gus will have to keep them alive to continue meth production.

Season 4

Jesse kills Gale. Victor arrives soon after and brings Jesse back to the lab. Mike and Victor keep watch over Jesse and Walt while waiting for Gus. Knowing he was recognized at Gale's house, and hoping to demonstrate that he can still be useful to Gus, Victor begins producing a batch of meth, revealing that he has learned the process by watching Walt and Jesse. Gus arrives, kills Victor in front of Walt and Jesse, then tells them to get back to work. Mike increases security at the lab, including installing video cameras and personally standing watch over Walt and Jesse while they work.

Mike informs Gus they may be able to drive Walter and Jesse apart. Gus agrees, and Mike takes Jesse with him on dead-drop retrievals and other tasks. Jesse foils a prearranged attack on Mike, boosting his confidence and increasing his loyalty to Mike and Gus. After another Los Pollos Hermanos truck is robbed and the meth stolen, Jesse aids Mike in retrieving it. His competence convinces Mike and Gus to continue making use of Jesse, and he goes to Mexico with them for a meeting between Gus and the cartel leaders that is intended to end their dispute. Jesse produces a superior batch of meth on his own, and Gus offers to have him stay in Mexico to produce it for the cartel. Jesse is apprehensive, but the offer is a ruse. During a party at Don Eladio's house to celebrate the rapprochement, Gus uses a poisoned bottle of tequila to kill most of the cartel leaders, including taking the first drink himself to alleviate suspicion. Mike is shot helping Gus escape, and Jesse helps both the ill Gus and injured Mike make their way to pre-planned medical treatment. For the doctor Gus has hired, Mike's wounds are secondary to Gus' illness, and after Gus recovers, Mike remains in Mexico for several weeks while Gus and Jesse return to Albuquerque. While Mike is recovering, Walt engineers Gus's death, after which he and Jesse destroy the meth lab.

Season 5

Mike learns of Gus' death and intends to kill Walt in retaliation. As Mike drives back to Albuquerque, he encounters Walt and Jesse, who explain why they killed Gus. They remind Mike that the security camera footage from the lab can implicate both Mike and them, and ask for his aid in destroying it. Mike tells them the recordings were stored on Gus' laptop, which is now in police custody. He aids Walt and Jesse to build and employ an electromagnet that wipes the laptop's data. This inadvertently leads the police to discover hidden account numbers and access codes for the money Gus deposited offshore to be used to pay the members of his organization for their silence. They seize the accounts, making it likely that Gus's former employees will reveal Mike, Jesse, and Walt to the police.

Mike joins Walt and Jesse in a new organization, with Jesse and Walt producing meth in a mobile lab operated inside the tented homes of a fumigation company's customers. When Lydia suspects the DEA is tracking the methylamine Madrigal supplies, she provides Mike, Walt, and Jesse with information on a train that includes a tanker car of methylamine. They arrange to steal a large quantity without detection, but Todd, an employee of the fumigation company who aids in the robbery, shoots and kills a young boy who witnessed it. Wanting no part of this brutality, Mike and Jesse sell their share of the methylamine to Declan, a drug dealer from Phoenix, while Walt produces the meth Declan distributes. Mike agrees to continue paying Gus's former employees from his share of the methylamine sale in order to ensure their continued silence.

The DEA identifies Mike's connection to Gus, but he removes evidence from his home and hides getaway money in a "go bag" at the airport, so a police search of his home turns up nothing. The police identify the attorney Mike has been using to make the payments to Gus' former employees, then locate the money he has been saving for Stacey and Kaylee. Intending to flee, Mike asks Saul to retrieve his go bag. Walt retrieves it instead, and meets with Mike. Intending to have Mike's associates killed in prison to protect his identity, Walt demands their names in exchange for the bag. Mike refuses and Walt shoots him with the gun from the go bag. After following a mortally wounded Mike to the edge of a river, Walt realizes he could have simply asked Lydia for the names. As Walt begins to apologize, Mike stops him, saying "Shut the fuck up, and let me die in peace", before collapsing and dying by the riverbank. Walt and Todd then secretly dissolve his body in acid.