A string of poisonings leads Jack & Dan to a deadly visitor.

Dan's police interrogation techniques come back to burn him when it is ruled by the court that his interrogation of a drug smuggler was illegal. As a result, the felon busted by Jack and Dan months before is set free. Without access to any department resources, Dan vows to put away the entire drug smuggling ring with just his pocket money. Along the way, the partners find themselves trapped in a truck full of scented candles, Jack is reprimanded in front of his ex, and Jack and Dan get stuck in the middle of yet another shoot out.

Dan's attempt to enliven a boring work day has chilling effects. Reusing evidence from a cold case file to jumpstart his auto investigation, Dan puts himself and Jack in the midst of a huge gun-running ring. Not only guns are discovered as a murder from 10 years ago surfaces.

A bank heist is in the works, but no one can seem to find the alleged thieves. As the Dallas PD searches the big city, Jack and Dan go out on their own in the opposite direction. They are running counter to their entire department, based mainly on intuition and a theory that the bank drama is just a decoy for a much bigger job on the other side of the city.

Dan enters the world of organized crime to catch mobsters who eluded him years ago. Things go awry though, when his undercover sting operation brings out two brand new groups of criminals. Dan will need Jack's help and a whole lot more to deal with so many dangerous mobsters and ultimately put the original ones behind bars.

Dan goofs up when he accidentally outs a witness in the Witness Protection Program. While a hitman from a dangerous crime family searches for the witness to keep the testimony buried, Jack and Dan team up with a U.S. Marshal to protect the innocent and stop the bad guys' nefarious plot.

Jack and Dan are suspended for their carelessness, so Dan "borrows" from the Narcotics Division to fund an off-the-books sting. When the unauthorized activities accidentally end up financing a prison break, Jack and Dan must capture the prisoners before they get too far and anyone finds out.

Jack and Dan go off on their own, yet again, after they are assigned to help a forensic specialist with a burglary case. Weary of the specialist's superiority complex, the duo breaks free only to be tangled up in another case entirely. They must get help from an unlikely source to save Liz when she gets in trouble working a high-profile prostitution sting.

Jack and Dan get a tip from a neighborhood kid about a lowlife stealing mail. During the investigation, they come across two identity thieves forging documents for a murderous pair of Mexican drug-runners, killing their way to better lives in America

After the ex-governor’s son, who was rescued by Dan and his former partner 25 years ago, is kidnapped by drug dealers, Dan is framed for the crime and forced into hiding. With Dan on the lam, Jack must find the real kidnappers and prove his partner’s innocence, while Dan, out of options, must turn to an old partner, the legendary Frank Savage for help

Jack’s uncle, Nate, a deceitful con man, witnesses an arson and goes to see Jack and Dan with information about the people behind it. With the Nate as the only witness, the investigation forces Jack to work alongside his uncle, a man he barely knows or trusts.

Jack and Dan investigate a spurious inspection report at a corrupt oil company only to discover that they might have actually stumbled onto a deadly criminal conspiracy with Liz’s boyfriend Kyle stuck right in the middle.

While investigating a stolen painting at a doctor's house, Dan faints, and is restricted to desk duty until he recovers. Despite the handicap, Jack and Dan must find and capture the mysterious art thief, who may have left more at the crime scene than he intended.

Liz and Jack's romantic getaway goes awry when Jack becomes suspicious of a bed-and-breakfast owner and Dan comes out to join the investigation.

While following up on a stolen truck investigation, Jack and Dan wind up uncovering a major heist involving a shipment of high-profile diamonds. Meanwhile, tensions rise when Dan discovers Jack is interviewing for a position on an elite police unit.

Dan is investigated by an arrogant Internal Affairs agent with a personal axe to grind. Meanwhile, Julius is hunted down by the guys he snitched on thanks to the IA agent letting them go.

Jack's former partner George Jenkins, who is now the department deputy chief, gets involved when Liz's informant against a member of the mafia is murdered and it is believed a corrupt cop was involved. Dan's former partner Frank Savage also aids in the investigation.