Mike helps a minister find his runaway teenage daughter who was lured to Philadelphia by an online child predator.

Mike comes to regret helping a gambler who owes money to a bookie; Marcellus requests his old partner's assistance in apprehending a suspected killer.

Mike comes to the aid of the wife and daughter of a cop who are fleeing the violence of their home, and finds them temporary refuge at Saint Victor's. After Grizz tells the wife that Mike's a former cop, she flees to New Jersey where Mike quickly tracks her down. Upon their return to Philly, Marcellus arrests them for kidnapping but is forced to release them when neither one will reveal the whereabouts of the little girl. Marcellus connects Mike with the cop, who tells a story that resonates uncomfortably with Mike's recollection of his own behavior, which is confirmed by his son. Troubled, he talks to Grizz and then follows his advice to make amends with Heather. When Mike sets a trap to discover the truth about the cop's abuse, he finds that the truth is not always what it seems.

Mike's efforts to help his friend Vanessa get her brother Teddy off the streets and off drugs puts all of them in danger after Teddy steals a dope dealer's $15,000 stash. When Mike strikes a bargain to spare their lives in exchange for paying the dealer the wholesale price of the drugs, he discovers that Teddy has stolen all of Vanessa's money, as well as the drugs provided by Marcellus to bust the dealer. Mike is forced to come to the painful realization that going to prison may be Teddy's only salvation.

Mike takes a job chauffeuring loanshark Jack Shannon, but begins to have doubts about the wisdom of doing so after Grizz and Marcellus warn him that he's headed down a slippery slope. After he's goaded into beating up a man to collect on a debt for Shannon, Mike realizes that his friends are right that he's headed for trouble, and tells Shannon he's quitting. Shannon tries to entice him to stay by offering to call in a favor with the District Attorney and have the case which led to Mike's dismissal from the force thrown out. Although he's sorely tempted, Mike turns Shannon down. After Mike leaves, Marcellus appears and is greeted warmly by Shannon.

After Marcellus frames bookie Nick Bennett for smuggling guns and Bennett's wife asks Mike to help clear him, Mike discovers that Jack Shannon is blackmailing Marcellus and using him to extort Bennett. Mike arranges a sit-down between Bennett and Shannon, tricks Shannon into confessing to a crime, and uses the confession which Marcellus has captured on tape to blackmail Shannon into cutting Bennett and Marcellus loose.

When a homeless man dies in his cab, Olshansky sets out to find the man's estranged family.

After Mike picks up Chuck, a frantic naked man, he helps him track down the prostitute who robbed him of his clothes, money, and most importantly, his wedding ring. They find Anna, the prostitute, who tells them that Raymond, her abusive pimp, has taken Chuck's belongings. Sympathetic to her plight, Mike offers to buy Anna's freedom from Raymond in addition to Chuck's wedding ring. After Raymond returns his ring, Chuck decides not to pay the $5000 Raymond wants for Anna, and sets Mike up for arrest. After Grizz bails him out, Mike fights Raymond to help Anna escape. Chuck finally tells the police and his wife the truth. Even though she throws him out, he's determined to win her back. Mike takes Chuck's $5000 and pays off Grizz's debt to a loan shark, which eliminates Grizz's need to ""borrow"" money from the collection plate.

Mike picks up a man who has just been given $10,000 to help an immigrant mother reunite with her lost child. When the fare leaves the money in the backseat of the cab, Mike experiences a night of manic complications trying to return it. He takes a woman in labor to the hospital, and later reunites her with the absent father; his cab is towed; he's hauled in by the police; and he enlists the help of a pair of street hustlers peddling fake Rolexes in an effort to assist a woman who is being blackmailed. When he finally hooks up with his passenger and returns the money, we discover that the man is a con artist who is using the money to play high-stakes poker.

Olshansky becomes the bodyguard for Abby, a woman terrorized by a stalker that neither she nor anyone else has ever seen. The signature item he leaves is a red rose. After Olshansky and Abby have a tryst, Olshansky tells her it can't continue. The next day, someone shoots at Olshansky -- is it the stalker, or is it Abby, and the stalker is a figment of her imagination?

Mike helps a Department of Justice employee whose sister has been kidnapped by a hitman who wants information about a banker in the Witness Protection Program who is scheduled to testify against the drug dealer whose money he laundered.

Marcellus gets a new partner, Aldo Rossi, and Mike has trouble adjusting to the change; after initially resisting Heather's suggestion that he reconcile with his father on his upcoming birthday, Mike finally relents, but his father rejects both his present and Mike; the ""Inquirer"" reporter who wrote the story of Mike's arrest now wants to paint him as a hero, much to Mike's disgust; when his friend Doug is killed in a hit-and-run accident after he gets out of his cab, Mike promises Doug's son Bobby that he will find the man who killed his father; after finding out that Doug had uncovered a fraudulent scheme at his company, Mike suspects that the company's chief financial officer had a hand in his death, and has mixed feelings when he is proved wrong by Rossi, who uncovers the real culprit.

Mike Jr. is upset when he sees a copy of his parents' divorce decree and gets into the sacramental wine at St. Vincent's, leading Mike to realize the importance of spending more time with his son; Grizz's high school sweetheart comes back into his life when she divorces her husband and comes to work at the parish; the cop who arrested Mike is mounting a case against Marcellus and asks Mike to flip on his former partner; when the cop's son is murdered during a robbery, Marcellus is assigned the case, which goes cold when the only witness is murdered; Mike and Marcellus join forces to find the cop before he administers some street justice to his son's killer; Marcellus offers to help his nemesis cover up his execution of the killer, but the cop declines and turns himself in, giving Marcellus a chance to get out from under his corrupt behavior.

Heather, Mikey and Grizz keep vigil as Marcellus and the rest of the force hunt down Johnny Scanlon, who has kidnapped Mike and threatens to execute him at the exact same as Johnny's brother Jimmy is executed by the state because Mike precipitated the incident many years before which led to Jimmy's killing a cop.

Romantic feelings resurface between Olshansky and his high school girlfriend as he reconnects with her while trying to help her schizophrenic sister.

A burglar that Mike once put in jail fears a third strike conviction if he reports that he witnessed a murder as he lay in wait to rob an office, and he goes to Mike for help in convincing the police that the wrong man has been arrested for the crime. The detective on the case has a long-standing grudge against Mike, so he does an end run around her by enlisting Marcellus's help. When they discover that the perp is an undercover cop, they are forced to devise a plan to trap him into confessing.

An exhausted E.R. doctor's error results in a man's death, and an upset Heather seeks Mike's help when the hospital administration refuses to take action after she reveals that the doctor falsified the man's chart to cover up his mistake; Mike convinces a reluctant Heather to give the story to reporter Emily Carson, whose investigation results in Heather's being fired and blacklisted on a trumped-up charge; Mike's concern that Heather may have to move far from Philadelphia with Mikey to find work puts a strain on his budding relationship with Faith, who begins to doubt that Mike is over Heather; Mike enlists the help of Ryan Ambrose, a psychiatrist at the hospital who supports Heather, in obtaining information that convinces the E.R. doctor to back up Heather's account of the patient's death and to admit his mistakes to Emily; Heather is reinstated, and she and Mike realize that it's over after spending the night together, leaving Mike free to commit himself to a relationship with Fait

After Mike convinces Marcellus to help him work to free a man they incorrectly helped send to prison, he incurs the further wrath of his father; Mike has mixed feelings when he discovers that Heather is seriously dating Ryan, who begins to provide Mikey with perks that are way out of Mike's league; Grizz assures Mike of his son's love, and Mikey confirms that for his father.

After Bill Olshansky has heart attack which creates irreversible and uncurable heart damage, Mike's decision to take care of his father leads them over rough territory as they hash out old grievances and can't seem to connect; in an attempt to get them to reconcile, Faith provides some words of wisdom for both father and son which finally enables them to bridge the gulf that separates them before Bill dies; picking up on Mike's feelings about Ryan, Mikey begins acting out towards the new man in his mother's life; Grizz is suspended by the bishop after $2,000 is missing from the collection money; Mike enlists the help of Aldo and the altar boys in exposing the real thief; Grizz contemplates leaving the priesthood in the face of his growing attraction to Beth, coupled with the bishop's lack of confidence and support.

Starting out fresh, Mike puts some distance between himself and Marcellus, grieves over Grizz's transfer to New Orleans, and moves into a new house, where he meets his energetic new neighbor, Liz Garza, who turns out to be an ex-nun turned probation officer; Jamie Farrell, a young man with a troubled past who isn't quite what he seems, enlists Mike's help after he witnesses a quadruple murder and is pursued by the D.E.A. agents who committed the crime; Mike seeks out Marcellus for information, and is warned to steer clear; risking his career, Marcellus saves Mike and Jaime from certain death at the hand of the agents; faced with a serious illness, Marcellus reaches out for Mike's friendship.

Mike and Marcellus work together to free an innocent man caught up in the nightmare of being falsely accused of terrorism by an F.B.I. agent who runs amok under the cover of the so-called ""Patriot"" Act when bombs go off at the Criminal Justice Center; in a misguided attempt to help, Jaime uses Mike's computer to hack into the F.B.I.'s database, which only leads to landing Mike in custody as well; Mike uses his time in custody to figure out that the bombings might be personal rather than institutional attacks, and gives Jaime the opportunity to redeem himself by having him hack into the PPD's database to find the link between the victims, who ends up being an ex-con out to destroy the people responsible for putting him behind bars; Mike and Marcellus track the bomber down just in time to prevent him from harming the next victim on his list, his probation officer, who turns out to be Mike's neighbor Liz.

Bettina's client Brian is released on a technicality after being accused of murder, and he seeks Mike's help in finding out who actually committed the crime so that his name and reputation can be restored; Marcellus undergoes surgery and gets good news from his doctor and a rebuke from Deborah for keeping his condition hidden; Liz helps Brian find a job and place to live when his employer and his wife abandon him; Jamie uses his street skills and some fast talking to provide Mike with an impressive vehicle in his search for information to support Brian's story; when he unearths information about the victim which reveals that she and her family were not who they appeared to be, Mike traps the murderer and clears Brian's name; as Mike arrives to take him home from the hospital, Marcellus is shot by a man posing as an orderly.

While Mike identifies the man who shot Marcellus as someone who escaped from a drug dealer take-down long ago, a second attempt on Marcellus's life points to the possibility of two different shooters; forced to hide out from some bad guys, Jamie temporarily moves in with Mike, and Liz teaches him how to be a good neighbor.

After Mike saves Leda Mills from three would-be rapists, she decides that the only way she can regain control of her life and prevent her attackers from hurting other women is to hunt them down and murder them; Marcellus helps a teenager being neglected and corrupted by his drug-addicted father; Mike is horrified when Leda phones him after the first murder to thank him for being her inspiration, and works with Marcellus to stop her killing spree, but it's Liz's insights into her behavior that give them the key to her capture.

Mike helps an amnesiac regain her memory to uncover who has marked her for murder; working with Mike, Jaime uncovers her unsavory past, but not before Mike falls for her; Jamie pretends to be Marcellus to impress a girl he meets online, and Marcellus goes along with it, in exchange for Jamie's painting his kitchen.

On the anniversary of his brother Rick's death, Jamie decides to meet with his father, Richard Farrel, in an attempt at reconciliation and instead discovers his affair with a young woman named Cate Rawlings, who is later found murdered; at Jaime's request, Mike attempts to find out what evidence Marcellus has on the murder without revealing Richard's affair with Cate; after Jamie breaks into Cate's apartment to remove evidence implicating his father, he's arrested and unwittingly gives Marcellus the information he needs to charge Richard with the crime; even though Marcellus is angry that Mike deceived him about Richard, the former partners work together to uncover the evidence that clears Richard of the crime; Jaime is devastated when Richard rejects his efforts at reconciliation once his name is cleared.

A young girl who witnessed a murder seeks Mike's help in helping her evade the corrupt police officer who has been paid off to cover up the crime and silence her; Marcellus takes up residence on Mike's sofa as his marital problems continue.

While Mike is more than willing to assist Jamie in turning a teenage friend away from prostitution, Liz is much less sympathetic to her plight until Jamie convinces her that the privileged upbringing he and the girl shared is no protection against pain; continuing to mentor Cal, Marcellus strikes a bargain with a loan shark to arrest his competition on the street in exchange for his releasing Cal from his crew; Mike walks on eggshells in the face of Liz's anger; after Liz manages to get Cal out of the shelter and into a foster home, Deborah agrees to let him stay at the Washington house until his foster placement goes through even though things are very much strained between her and Marcellus; Mike, Marcellus and Liz use their individual talents to get Jamie's friend out of the hands of her pimp and into the arms of her parents.

After Liz asks Mike to look into the death of the girlfriend of her fireman friend Nick, Mike comes into conflict with Nick's boss, who's an old nemesis; Marcellus works the case from a pattern-killing angle, linking it to a similar murder 2 years ago, and discovers that the otherwise unconnected victims had the same locksmith; Mike discovers that a fire that Nick's squad recently fought was in a building that housed a methadone lab where $112,600 disappeared, and suspicion points to the squad.

After Jamie and his friend Wilson are jumped by gay-bashing thugs and the beat cops are reluctant to take the crime seriously, Mike enlists Marcellus's help in obtaining reports of other assaults in the area to determine if the cops are failing to report hate crimes properly; Marcellus becomes concerned about the future of his marriage when he learns that Deborah has been seeing another man; Wilson is murdered after he recognizes one of his attackers, and Mike finally uncovers why the beat cops were reluctant to file complete reports that could point out patterns in the gay-bashings in their district.

Mike steps in to help his cousin who's caught a downward spiral of addiction and suicidal urges as he combats post-traumatic stress after serving in Iraq.

Mike uncovers an illicit adoption ring trafficking in stolen babies when he grudgingly agrees to help one of Liz's clients, a former addict who's turned her life around, in the search for her missing child; Marcellus calls an end to it when he realizes that his obsession over the new man in Deborah's life has gone too far.

When Mike attempts to return the cell phone a stripper named Molly leaves in his cab and discovers that she's disappeared, he sets out to find her for the sake of Quinn, her twelve year old daughter; Marcellus's old friend and mentor Henry Baker asks his help in investigating how his jobless grandson Darryl has such an endless supply of cash; Quinn and Marcellus provide Mike with the inspiration and information he needs to find Molly, who's been kidnapped by one of the partners in the law firm where she works during the day as a paralegal; after Marcellus discovers that Darryl is linked to a series of high-end burglaries, he offers to sweep it under the rug, but Henry refuses to allow Marcellus to cover up the boy's crimes.

As Mike and his passenger exchange ""she done me wrong"" stories, he reminiscences about the time he almost fell for the charms of a greedy woman whose doctor lover deceived her husband into believing that he was dying. Marcellus arrests her lover for helping her husband arrange for a hitman so that his wife could collect on the double indemnity clause of his life insurance policy, but is unable to file charges on the woman both Mike and Marcellus believe was behind the entire plot.

When a drug dealer framed by Mike and Marcellus after they were unable to arrest him legitimately is released from prison, he begins to wield a path of destruction through Mike's life, endangering Liz and Jamie; Mike and Liz decide to move their relationship forward.