Season 4

Patrick, the owner of Buster's Beach House in Long Beach, California is concerned about his bartender named K.P. and the large loss of alcohol. The Mystery Diners not only confirm that K.P. is stealing money from him and conducting a scam by counting lemons slices, but they even discover bigger problems with his executive chef named Johnny. He has been responsible for sexual harassment cases along with showing preference with the female wait staff and a few restaurant regulars. During the confrontation, Johnny and K.P. are confronted and fired by Patrick. In his exit interview, Johnny is remorseful for his behavior and plans to make reparations for his actions. The narrator revealed K.P. still maintained he did nothing wrong and has moved on to new employment. Johnny has apologized for his behavior and is seeking counseling. Patrick has hired a new executive chef and bartender.

After losing several sushi models, Bruce, the owner of Lotus on Flower in Los Angeles, fears that one of his best customers is behaving inappropriately during the restaurant's "naked sushi" dining experience. Charles sends in Mystery Diner Christine to go undercover as a model to discover who is encouraging the inappropriate behavior.

Michael, the owner of Newport Beach Brewing Company in Newport Beach, California, asks Charles to investigate his onsite brewmaster who is suspected of running a side business. The Mystery Diners go undercover and discover that his brewmaster is not behind the side business. Instead, they discover big problems with his bartender Mike who is running a side business with a waiter. The bartender admits to brewing his own flavor brands of beer from his own home and promoting it in the Newport Beach Brewing Company. During the confrontation, Michael fires Mike. In his exit interview, Mike remained unremorseful for his actions claiming that Michael lost an opportunity to market and sell his flavor beer brands that could've helped his business. The narrator revealed that Mike has been unsuccessful in promoting his own beer. The waiter has also been terminated for his involvement and has found employment elsewhere. The brewmaster continues to be a valuable employee.

The owner of Colombo's Italian Steakhouse in Eagle Rock, California, fears an Employee of the Month competition is the reason for a lack of staff harmony. The team proves this because of a 4-time Employee of the Month-winning waitress. She has been badmouthing her co-workers and sabotaging a waiter by throwing away his ticket orders as soon as they're printed.

After nearly losing his life during a paragliding accident in Brazil, the owner of Gauchos Village in Glendale, California is finding discrepancies in his revenue and inventory since his return to the business. He believes that his chef is involved. The Mystery Diners go undercover and discover the chef is not behind the discrepancies. Instead, they find big problems with the manager who is behind the discrepancies and missing inventory. He has taken advantage of his absence by badmouthing him to the staff, letting women take leftovers home (which is against normal practice of a churrascaria), selling meat to the staff, and using it and the restaurant's alcohol to host a barbecue at his place. During the confrontation, the manager claimed the alcohol and the meat were meant to be used as a surprise barbecue for the owner. He doesn't believe the manager's claims and fires him for it.

The owner of Bistro Bordeaux in Evanston, Illinois investigates several complaints about his new executive chef. The Mystery Diners discover that the new executive chef is not responsible for the actions that the complaints were about. It was discovered that a disgruntled sous chef who believes that he should've been the executive chef. As a result, he bad-mouths him to the whole staff when he turns his back, telling guests that he is the executive chef, and tainting the food so the executive chef can be fired and he can step into the position. When both are confronted, the sous-chef tried to defend his actions. Stiles points out that he is the last person who should be executive chef after he was caught on tape sabotaging the chef's orders, making negative comments to the wait staff and lying about it to cover up his scam.

The owners of Big and Little's Restaurant in Chicago, Illinois respond to rumors that employees are illegally selling alcohol to customers at their restaurant. The Mystery Diners discover bigger problems with their manager doing a side business in selling alcohol with his friend Enrique where the sales nearly attract the attention of the police. During the confrontation, manager is fired from his position and is told to inform his friend to never return. The narrator revealed that the former manager and Enrique were never heard from again. Those who were involved were either reprimanded or terminated.

The owner of Cheesie's Pub and Grill in Chicago, Illinois is concerned about cheating with his grilled-cheese-eating contest (too many petite women among the winners) and cost of his alcohol sales. The Mystery Diners point to bigger problems with his waiter and his cashier cheating to help the female contestants win and giving away free beverages. In spite of his waiter's pleas that it was good for Cheesie's during the confrontation, he and the cashier are fired. The narrator revealed that both former employees have apologized for their actions and moved on to other jobs. The owner has implemented new rules for his grilled cheese-eating contest to discourage cheating on both the customers' and staff's part.

The owner of Bella Luna Café in Chicago, Illinois contacts Charles Stiles because he is hearing customer complaints with his delivery service. The Mystery Diners not only point to one of the delivery serviceman not doing his regular routines when he had to do some errands in between his deliveries, but another serviceman who is charging extra delivery fees, eating delivery food, insulting customers who refused a messed up order, and showing road rage. While one of the serviceman is reprimanded for his actions during the confrontation, the other delivery serviceman is fired. The narrator revealed that the former serviceman has started working at another restaurant. The other serviceman stopped doing errands during his job.

The owner of Gigi's Restaurant in Philadelphia, Pennsylvania is concerned with rumors about his mother and co-owner discriminating younger customers. The Mystery Diners go undercover and discover that his mother is not behind the discrimination. Instead, he discovers big problems when the waitress was behind the discrimination with the belief they are too frugal. During the confrontation, the owner calls her out for the discrimination and she is fired. In her exit interview, the waitress remained unremorseful for her actions wanting better customers who are rich to pay for her services. The owner later apologized to his mother after seeing that she was trying to repair the damage with their customers that the waitress caused. The narrator revealed that the former waitress has started working at another restaurant. The owner's mother continued to work alongside him at Gigi's.

The owners of Del Rossi's Cheesesteaks Co. in Philadelphia, Pennsylvania has been hearing complaints about their recently-hired security guard they called "Fury" (who was a family friend) being too rough with customers and being bossy with the staff. The Mystery Diners not only confirm this, but also point to bigger problems with one of their cashiers taking advantage of Fury by sneaking into the kitchen and stealing from the restaurant. During the confrontation, the cashier is fired and Fury is reprimanded and put on probation. In his interview, Fury is remorseful for his actions and promises to change his attitude. The narrator revealed that the former cashier has paid for the items he stole. Fury has adopted a more friendly approach in his job.

Bob, the owner of Venture Inn in Philadelphia, Pennsylvania, is hearing complaints from both his regular and cross-dressing customers that the weekly quiz night is rigged. He suspects his manager is involved. The Mystery Diners discover that the manager Joe is not behind the rigging. Instead, it was the bartender who has stolen the answer sheets in Joe's office and giving them to a reigning Drag Queen champion named Brigette Jones, via an ear phone in her ear. When confronted by Bob for rigging the quiz night, the bartender is fired for being behind the scam and is to inform Brigette Jones to never return to the restaurant. In his exit interview, the former bartender maintained he did nothing wrong and mentions that he hopes Stiles is happy for firing an innocent man. Joe is spared when Bob realized he had nothing to do with the rigging.

Marvin, the owner of Falls Taproom in Philadelphia, contacts Charles Stiles after hearing rumors of a feud breaking out between his girlfriend/manager and his best friend. The Mystery Diners point to bigger problems with the owner's friend and regular customer behind the rumors. Showing up intoxicated, he had been harassing customers and the manager. When confronted, Marvin ends his friendship with his friend and bans him from his bar. In his exit interview, the former friend expressed his remorse in his behavior and plans to make up for his misdeeds. Marvin later apologizes to his girlfriend, who will only forgive him if they go out shopping the next day