A man who looks just like Monk crosses the street in Los Angeles, is hit by a bus, and dies.
A deliveryman stops by to drop off Monk’s new refrigerator. He points out there’s a lip in the floor and that he has to charge as if it were a step. Monk tries to assert himself but fails miserably despite Natalie’s encouragement. They’re interrupted when the FBI calls and requests a meeting with Monk at the police station. FBI Agent Stone meets with Monk, Natalie, Stottlemeyer, and Disher, and explains that he needs Monk to come to Los Angeles. Mob hitman Frankie DePalma was killed by a bus while on his way to his hotel to meet with a mob boss to get his next assignment. They don’t know who DePalma was after or who he’s working for, but they’ve managed to keep his death out of the papers. DePalma looks exactly like Monk and they need the detective to impersonate the hitman and find out the vital information. Stottlemeyer refuses to let Monk endanger himself but Stone insists that someone will die if Monk doesn’t help.
Monk goes to FBI Headquarters in Los Angeles and memorizes DePalma’s life. However, as soon as he realizes what he’s doing, he forgets everything. Stone has no choice but to convince Monk that he can get into the role and shows him how to swagger like a hitman. Monk dresses in DePalma’s clothing and goes to the hotel, where the staff greets him as DePalma. The detective gets to DePalma’s room and uses a hidden wire to contact Stone and the others outside in a surveillance van. Monk proceeds to tell them what he’s doing… step, by step, by step.
As Monk finds DePalma’s gun in a hidden suitcase compartment, an attractive woman, Lola, enters the hotel room. She comes onto Monk and when he keeps her at arms’ length, she figures he’s mad at her. She orders champagne and Monk almost gives it away when he refuses to tip the waiter, but he manages to give the man a twenty. Monk claims he’s giving up alcohol so he doesn’t have to drink the champagne, and then asks who he’s been hired to kill. She says they’ll both find out that night. When Lola tries to kiss him, Monk backs away and claims that he has a girlfriend, Natalie. Lola tells him to bring her to the nightclub that evening where they’ll meet with Jimmy Barlowe, the man who owns the club and who wants to hire Monk.
Natalie, wearing an evening dress, goes with Monk to the club. Monk asks the bartender to turn down the loud music and he refuses, until he realizes who Monk (supposedly) is. When a customer comes over to complain, he quickly backs down when the bartender tells him Monk is Frankie DePalma. Monk starts to get into the role as Lola comes over and separates him from Natalie. She takes him to meet Jimmy, his nephew Lenny, and lieutenant Tommy G. They make small talk and Tommy G says that they met three years ago in Miami. Monk manages to bluff it out and even scares Tommy G by straightening his tie when he asks about one of DePalma’s kills. Jimmy finally comes out with it and says that a Stanley Greenblatt lives in Ventura, and he wants DePalma to eliminate him. Unfortunately, things get awkward when he hands around cigars. Monk manages to bluff his way through again, saying he prefers to smoke them with the tips still on. Lenny, who wants to kill Greenblatt himself, starts to suspect something is up.
Later, Monk and Natalie meet with Stone, Stottlemeyer, and Disher. They can’t connect Greenblatt, an old man, to anyone in the mob. Stone asks Monk to keep up the impersonation until they learn something useful and he reluctantly agree. Stottlemeyer and Disher volunteer to talk to Greenblatt and see if he knows Barlowe. Greenblatt wants nothing to do with them, insults them, and throws pans at them until they leave.
Monk meets with Tommy and Lenny for breakfast on the beach. Monk claims he’s taking his time, and Tommy G explains to an impatient Lenny that DePalma is a methodical man. They’re interrupted when Monk’s nemesis, Howard Krenshaw, comes over. He’s on vacation in Los Angeles and is surprised to see Monk out of his house. He refuses to go away and Monk, now fully into his role, shoves him away and warns him that if he doesn’t leave, he’ll kill him. After Harold slinks away, Monk snaps at a nearby couple in a very non-Monk kind of way.
Back at FBI headquarters, Stottlemeyer warns that Monk is too much into the role and Stone is ready to pull the plug. Monk, playing the role of DePalma to the hilt, refuses to back down and insists that he has to go through with the impersonation to keep Greenblatt from being killed. Natalie thinks he’s finally found an outlet for years of repression but Monk says he’s in control. When he tries to leave, Stottlemeyer tries to stop him but Monk stares him down and orders him out of the way. Stottlemeyer, surprised, steps back and lets his friend leave.
Monk returns to the hotel and confronts Lola, who tries to flirt with him. He demands to know why Jimmy wants Greenblatt dead. She finally admits she doesn't know and succeeds in kissing Monk. He panics and starts to lose his assumed personality of Frankie DePalma. Lola realizes something is going on but before she can follow up on it, Lenny arrives and insists that Monk finish off Greenblatt. He insists on going along with Monk, who has no choice but to agree. They drive to Greenblatt's house and Monk goes in alone. He discovers that Greenblatt has died of a heart attack.
The next day, Natalie brings Monk in to apologize for Stottlemeyer. Stottlemeyer tells Monk that he's proud of him, and knows that his friends has the guts to stand up for what he believes in when it comes right down to it. Stottlemeyer figures there's nothing they can do because Jimmy never paid Monk and Greenblatt wasn't murdered. However, Monk notices that Stottlemeyer has received two birthday cards from his two sons. He remembers seeing two birthday cards from son to father at Greenblatt's house, but one of Greenblatt's sons, Alvin, supposedly died a year ago.
Here's what happened: Alvin embezzled money from one of Jimmy's casinos and then faked his death. Jimmy couldn't find Alvin so he decided to lure him out of hiding by killing his father Stanley and hoping Alvin would come to the funeral. Stone stakes out the funeral but Alvin doesn't show. They figure that Jimmy grabbed Alvin at the hospital.
Jimmy, Lenny, and Tommy G have Alvin at the night club and torture him until he reveals where the money is. Once they have the information, they prepare to kill him. Monk arrives, still acting like Frankie DePalma, and insists on fulfilling his contract and killing the son since he didn't kill the father. Lenny refuse but Monk coolly stares him down and Jimmy hands over the gun. As soon as he has it, Monk takes them captive as Stone and his men burst in to arrest them all.
Later, Monk deals with the refrigerator deliveryman again when the man refuses to honor the warranty on the ice maker. Monk tries to stare the man down and doesn't back down… but he doesn't succeed, either, until Natalie secretly helps him by adding her stare to Monk's. The deliveryman backs down and Monk figures that he's still got it.