After losing thousands of dollars in unaccounted alcohol and hearing rumors of late-night staff parties, Kim Brennan, owner of Big Earl's Greasy Eats in Cave Creek, Arizona, contacts Charles, and Mystery Diners Shellene, Bradley, and Chris go undercover as a waitress and customers, hoping to score invitations to an after-hours bash.
After noticing low revenue and receiving numerous staff complaints that his recently-promoted head waiter David is not evenly distributing the pooled tips, James LaGrappe, general manager of D'Cache restaurant in North Hollywood, California, contacts Charles and the Mystery Diners to help him discover whether the rumor is true.
When Mario Nasab, owner of La Traviata in Long Beach, California, has been receiving complaints from his customers about the quality of his fish, Charles and the Mystery Diners discover that Joe, a head chef inherited from previous ownership might not be honest about what's in his high-priced dishes.
Johnny Persico, owner of Pina Pizza House in Downey, California, has been noticing discrepancies in beer sales, as well as an increase in voided tickets and believes his "frat-tastic" college-enrolled waiter Jed may not have his best interests at heart and might be taking the party off-campus and into his restaurant.
Marc Sgrizzi, owner and head chef of Parma in Las Vegas, has been noticing discrepancies in sales receipts and inventory with his high-end Italian deli meats and suspects that two of his employees, Peter and Diane, who have full access to the restaurant, are responsible for these losses.
She is seen giving away free food and alcohol, reusing a promotion Will discontinued a few months earlier, ignoring women coming to the restaurant, and encouraging the waitstaff to take care of the men by setting up an unauthorized dating service that was not approved by Will.
When Stephanie Vitori and Danielle "D-Rock", owners of Cheeseburger Baby in Miami Beach, notice sales discrepancies, they ask Charles to investigate an ex-con waiter they hired named Guillermo to give him a second chance at life.
Arthur "King Creole" and Shawnette "Tambourine Green" Humphrey, husband and wife owners of World Famous N'awlins Jazz Café and Oyster Bar in New Orleans, have just opened their restaurant two months earlier and are getting complaints of poor customer service.
Mystery Diners Nicole, Andrew, and Damon go undercover as a waitress, a customer, and a seafood distributor, and discover that their manager Chastity has accepted unauthorized delivery deals and staffed the place with her friends, most of whom are not qualified, including bartender Sinae.
Mystery Diners Loree and Mark go undercover as a waitress and busboy, and catch Pamela coming to work late, making personal phone calls, and sleeping and eating on the job, but is actually honest in reporting a cash discrepancy to manager Mike.
In addition, head chef Johnny has been responsible for sexual-harassment cases unknown to Patrick and showing preference with the female waitstaff (he is also shown verbally abusing waiter Brian by calling him "Brianna", even after being told to stop).
After nearly losing his life in a paragliding accident in Brazil, Kevin Aksacki, owner of Gauchos Village in Glendale, California, is finding discrepancies in his revenue and inventory since his return to the business; he suspects that his general manager Miguel is responsible for these losses since he is in charge of ordering and receiving the food, as well as his chef Gabriel, who handles the meat.
Mystery Diners Siera and Destiney go undercover as a food runner and a customer, and catch manager Gregg charging an unauthorized $10 corkage fee for any outside liquors and doing a side business selling alcohol with his friend Enrique, who is posing as an employee of the restaurant; this nearly attracts the attention of a passing police car.
Chris Johnston, owner of Cheesie's Pub and Grub in Chicago, suspects his manager Joe, cashier Sara, and best friend/waiter Patrick have fixed his grilled-cheese-eating contest (there have been nine winners over the course of two months, and most of them are petite women), leading to a decline in alcohol sales (two hours of free drinks are part of the prize).
Bob Berkowitz, owner of Venture Inn in Philadelphia, is hearing complaints from both his regular and cross-dressing customers that the weekly quiz night is rigged and suspects that the 10-time Drag Queen champion Bridgette Jones is cheating and his manager Joe is helping her, since he is in charge of running the show.
Mystery Diners Vanessa and Robin go undercover as a waitress and a customer, and catch Kevin drinking on the job, stealing food orders by scamming Trevor, and selling a keg of Green Room to his frat brothers with Matt's help.
Jeff Levitt and Dave Martin, owners of Shades Oceanfront Bistro, a dog-friendly restaurant, in San Diego, discover discrepancies in their chicken and beef supply, and suspect that their head chef Clint is responsible for these losses.
Joleen, co-owner of an undisclosed restaurant in Culver City, California, contacts Charles to do a reverse sting on her ex-husband/business partner Tony, who has been abusing his position by making offensive comments about the waitstaff's physical appearances and stealing their tips.
With Amanda going undercover as a customer, the team sees Tony ridiculing Charlotte for her appearance, eating in the kitchen, selling foie gras (which is illegal in California due to being considered animal cruelty) and having head chef Eric cook it, smoking inside the restaurant, and pocketing the waitstaff's tips from large parties.
Mystery Diners Humberto, Jamie, and Kendall go undercover as a vineyard worker and customers, and discover Ricardo stealing empanadas (the employees are allowed to have the food on their lunch break, but they have to buy them from Damian's sister) and conducting a scam with Sean and Chris that involves selling the barrels to Julio.
The Mystery Diners discover that Kayla has not only booked the venue for two photo-shooting events and the fake wedding simultaneously, with her assistant Tony helping out in the set-up, but she has also been accepting kickbacks from a caterer named Scott, who is known for his shaky reputation.
Glen and Susan McIntyre, husband and wife owners of Gateway Restaurant and Lodge in Three Rivers, California, near Sequoia National Park, have been noticing discrepancies in food and alcohol costs and hearing complaints from their guests about theft and late-night parties taking place.
The team reveals that passenger service manager Jessica has been sneaking her friends onto the train past inattentive conductor Will, and that head chef Bryan has been stealing meat to help his brother save his failing diner in Santa Clarita.
Jamie Alba, co-owner of Sisley Italian Kitchen in Sherman Oaks, California (from "Cooking the Books," which has since relocated to Valencia), contacts Charles again to help determine if he should invest in a failing Torrance restaurant called Industry Sports Bar & Grill.
Meanwhile, head bottle service girl Caymen believes she is not getting paid enough and is working with an unidentified sausage vendor (who was told many times not to operate outside the club) to make extra money, causing the poor dinner sales.
While setting up a bait house operated by Mystery Diner Hal (who had previously appeared in "Daddy's Girl" and "Young Blood"), the team discovers that Chris, one of Cynthia's drivers, is the direct cause of the customers' complaints.
Charles' private investigator Melissa reports that she found a roll of packaging labels in the trash titled "Tree Brothers Bakerama," causing Luca to suspect that one of his employees is running a side bakery business and using the appliances in the warehouse to bake their products.
Mystery Diners Jamie and Elliott go undercover as a customer and a fundraiser Santa Claus (who has a permit), and reveal that manager Sammy is running a fake charity with an unidentified woman dressed as a street Christmas elf, who happens to be her friend.
Also, Charles' private investigator Dennis (who used to work for a Brooklyn precinct of the NYPD) reveals that waitress Mo was badly affected by Sammy's scam and had been secretly stealing toys for her own son from a real charity Nirav has been running as well, and has a problem with unpaid parking tickets.
The Mystery Diners count down the Top 10 favorite love-related scams that broke hearts as well as love delusions: Rose Melillo and Tom Kiermaier, owners of Belcourt Taps in Nashville, are hearing rumors that their songwriting contest is rigged.