After Jack and Dan investigate a break-in at a locksmith's shop and discover the burglar stole a tubular lock pick that enables the user to bypass most standard locks, Dan heads off to dinner with Andy Davis, the former governor's son who Dan and his ex-partner, Frank, rescued from kidnappers 25 years ago. The experience has bonded Dan and Andy for life.
As the two men exchange hugs, Andy cues the bartender, who slips Dan a mickey. (We see that Andy has previously met two men - Brody and Parker - at a motel and that they've promised him a cooler filled with marijuana if he'll help them take Dan down.)
Back at the station, Lt. Ruiz tells Jack that Andy has been kidnapped again - and Dan is the prime suspect because his fingerprints were found on the ransom note. (We see Brody and Parker have used the tubular lock pick to enter Dan's trailer, where he's sleeping off the sedative, and placed his fingerprints on the note.)
When Jack's phone call awakens Dan with this news, Dan realizes that he was sedated; he refuses Jack's request to come to the station and heads off to rescue Andy. But when a police sketch of Dan appears on the TV news, a woman spots him and calls the police.
As hapless Hodges leads the briefing, Jack voices his disapproval, telling Lt. Ruiz that Andy has been arrested 12 times since he was first kidnapped and that his ex-governor father has always gotten the charges dropped. Ruiz tells him to stick to the locksmith burglary case, but if that ties in to the new kidnapping . . .
Dan takes refuge in Jack's apartment and sadly prepares to shave the mustache that makes him so easily identifiable, but he's interrupted by the arrival of Jack, followed by Asst. D.A. Liz, who's slipping Jack the original files of Andy's multiple arrests. Jack attempts to shoo her away, pretending that he's with a woman, but Dan's female voice impersonation doesn't fool her, so he escapes out a window.
Jack questions a marijuana dealer who'd been arrested alongside Andy nine months back and - after threatening him with another bust - he learns that Andy's been buying drugs from Brody and Parker at that motel. When Jack arrives there, Andy panics and shoots Jack in the arm with the gun that Brody and Parker stole from the sedated Dan, enabling them to escape.
Meanwhile, Dan breaks into a home, falls asleep on a couch, and gets awakened by a golf club-wielding man. It's his now-retired former partner, Frank Savage! They embrace and Dan explains his situation, but Frank's wife, Cynthia, isn't happy to see Dan and orders him out. Dan begs Frank to help him. Frank says that he's in therapy and has moved on, but Dan notes that he still has his "bitchin' 'stache," while Cynthia calls the police. So Dan takes Frank hostage - using his ex-partner's old gun - and escapes again.
Dan and Frank share a laugh - that old "take your partner hostage" ruse still works! Frank slips into a vintage shirt and sunglasses. Reunited and it feels so good.
As Jack files a report on his shooting, he learns that the bullet came from Dan's gun. Upon hearing this, Liz realizes that she'll lose six cases where Dan was the arresting officer if he isn't cleared. Jack believes those cases contain information as to who's trying to frame his partner. Liz agrees, delivers the files, and Jack discovers that Dan had busted Brody and Parker at the motel where he was wounded.
Meanwhile, Brody and Parker have Andy locked in a room. His whining is driving them crazy. When Andy overhears their plans to kill him with Dan's gun, he escapes by kicking out an air vent.
Dan and Frank confront the bartender who slipped Dan the mickey, busting up the bar to get him to talk. He fingers his pot dealers, Brody and Parker, but all this glass-smashing has attracted the police. Dan and Frank run - straight into the just-arriving Jack's car - and they elude the uniformed cops. Jack explains that Dan had discovered Brody and Parker were using a tunnel underneath the Cotton Bowl as a grow space and he suspects that they've taken refuge there. So that's where they're headed.
Just as Brody and Parker discover Andy has escaped, Jack, Dan, and Frank arrive at the Cotton Bowl and spot Andy in the press box. Dan orders Andy to get on the roof, yelling, "Everest." Jack knows what this means - he's heard all of Dan's old war stories many times - and begins a hand-over-hand climb to the top of the press box while Dan and Frank take the stairs.
When Dan and Frank catch up to Andy, Brody and Parker are right behind them with guns drawn. As they order Dan to call for a helicopter to take them away, Jack jumps them from behind. Fists fly - Dan, Frank, and Jack subdue the kidnappers/dealers - and a panicked Andy runs, stumbles, and winds up dangling from a window. Frank and Jack eventually pull him to safety, and he's reunited with his family.
Back at the station, Lt. Ruiz notes a lock pick found on the criminals ties them to the burglary, so Jack's in the clear. Frank embraces Cynthia and returns to his life of retirement, while Dan embraces his new partner, Jack.