Prologue: Wojo books a young black man name Wendell Frazier on grand theft auto for stealing a police car. Both Wojo and Barney are surprised at this. Chano, Yemana, and Fish come back from a stakeout saying they blew it. Reluctantly, they tell Barney that they found a suspect carrying a large box. Fish yelled out the window for him to stop, but the window was down. Chano says he got out and yelled at the suspect to stop, but he fell down and Nick fell on top of him. Fish then leaps over top of them to chase down the suspect, but he got away. They did manage to get the box he was carrying, which had 20 kilos of marijuana, each in one kilo packages. Wendell says, 'Let's get some food!' Fish gets up and has pain in his lower back. Barney asks if he wants to see a doctor, but Fish insists he's fine. Wendell offers to buy the pot off him. Harris takes a call from Siegel's Department Store about a burglary. Wojo goes with him, but before they can leave, Nick comes running out of the bathroom saying Fish is out cold.
Part One: Fish tells Barney he has a kidney stone, but the doctor says that he is okay to return to work, so he will be back. He tells Barney that at times like this, he wants to be around friends. Nick calls him a sentimental fool. Wojo and Harris come back with a Mr. Holliman. He says the building must be the oldest police station he's been in. Harris says they are second, just a few minutes younger than Devil's Island. Harris tells Barney that Holliman had spent the weekend at Siegel's, and Wojo says they want to press charges for breaking and entering. Holliman explains that he had went there on Saturday to get some little food samples, but got sleepy and the store closed before he woke up. He says he slept in the executive washroom. He says he did eat some food, and he will pay them back when he gets his Social Security check, but all he did was watch the TV in the washroom. Barney asks why he didn't get out before he got found, and he says he overslept because he couldn't find an alarm clock. Wojo takes a call from a lieutenant from Narcotics about the pot they confiscated. Fish comes back and says that he has just a little kidney stone. He also has to drink fluids so he can go to the bathroom a lot. Wojo brings the box with the pot out and says there are only 18 kilos inside. Fish insists there were 20 kilos when they brought it in. Barney tells Wojo to look again. Barney thinks of the headline: 'Confiscated Drugs Missing From Police Station.' Wojo then comes limping out saying he was bit by a rat. Chano grabs a nightstick, then asks Wojo if he was kneeling on the floor. However, when Wojo says the rat raised up on his hind legs, Chano pulls out his revolver.
Part Two: Harris asks Fish if he is okay. He asks if it hurts when the stone comes out, then Fish says the doctor told him it was like giving birth. Sam Becker, from Becker and Son Exterminator, arrives to find the rat. He says they love old buildings, and can run up and down the walls for years. He hears a noise, and Fish gets up to go to the bathroom. Becker says he will be there all day. Barney asks if his son will be there too, but Becker says that he's the son; that his father died ten years before and he kept the name of the business on his truck. Chano says he's looked through mug books and can't find the guy who had the pot. Barney says they will catch up to him but he'd rather get his hands on the missing pot. Wojo comes back from the doctor saying he's fine too. He is worried about getting rabies. Becker says there hasn't been rat rabies in a long time, but warns about the bubonic plague. Wojo gets upset, but Barney tells him not to worry. Then he takes a call from the department store in his office. Holliman asks Frazier what he did with the car he stole and he says he gave it to his mother. Del Vecchio, a detective from Narcotics, arrives to get the pot. He introduces himself and picks up Fish's pill bottle. Fish introduces himself as, 'Fish. Diuretics.' Wojo and Fish nervously try to explain what happened to the missing pot. Barney tells Holliman that the department store won't press charges. Barney gives him 20 dollars under the laws of New York State. However, there is only $14.35 in the petty cash fund, so Barney says the remainder is time off for good behavior. Holliman tells Frazier, 'Don't let this fool you. Crime doesn't pay.' Wojo introduces Barney to Del Vecchio, who says just give him what they have. Barney insists that the circumstances are explained, but Del Vecchio says the less he says, the better. He implies that they may have kept it and Frazier tells him about trying to buy it from them. Barney insists they do things by the book. Del Vecchio says he believes them, but his face makes it look like he doesn't. He is about to take it out when Becker comes up with the missing two kilos. He says he found them behind the boiler in the basement. He also says that a big pack rat had it hidden and was eating out of one of the packages. Chano says that they come big in his building. Becker says the rat raised up on his hind legs and gritted its teeth at him. Wojo says it was the same one that bit him. Becker says he grabbed a shovel and hit him, and it lay there with a smile on its face. Del Vecchio puts the pot in the box and leaves. Wojo asks if he thinks Del Vecchio believes them and Barney says, 'Would you?'
Epilogue: Barney asks Harris if he is still in court. He says no, that Frazier would get a year's suspended sentence and two years probation. Wojo is assigned to the district attorney's office for the day and Chano and Nick are giving depositions to Narcotics. Frazier comes in saying he has information to give them. He wants 50 dollars for it but they say they will give him five bucks if they want it. Frazier says if they don't want it, they don't have to pay him. They say okay, and Frazier tells them that Fish passed his kidney stone, so they pay him.