Lily is undercover as the girlfriend of a young Irish mobster. She ends up agreeing to marry him in order to draw his mob boss father into a position to be arrested. Joe orchestrates the wedding as bait but it turns out Lily has to go through with it and marry the guy in order for them to get their man.

Joe and his agents infiltrate a dating service in order to catch a woman who is suspected of killing several of her past dates. Caroline Glenwood is a lethal temptress, suspected of murdering more than one of the wealthy men she has met through dating services. Joe, posing as a potential suitor, puts his crew in place posing as dating service employees in order to stop Glenwood before she kills again.

An FBI agent trains and handles agents who go under cover to solve crimes; Joe mourns the loss of one of his own as the dangers of the job become all too real.

Darnell and Heather go undercover to infiltrate a band of bank robbers making its way across the U.S.; Lily poses as a waitress to get the goods on a dirty judge in a case that gets personal for Joe.

Artie, Joe's friend, comes back into town, and offers Joe a business proposition. His plan is to dig a tunnel from a bookstore to the bank across the street right into the vault. Lily goes undercover as the bookstore owner to keep the customers distracted from what's going on in the basement with Joe and Bruno. Also, things get complicated when Joe's old flame shows up and wants to move in with him.

Joe and Lola use a dead body to weave a net for a known killer in order to find where he's buried the bodies; Darnell and Lily act as a couple on the rocks in order to create a diversion while the FBI plants a bug in a suspect's car.

Joe handles a ""black op"" for his FBI boss investigating the death of an FBI agent working undercover with the LAPD, investigating them for brutality under cover of the law. Darnell poses as a reporter, Lily as a medical student in the autopsy, and even Marcy returns to UC work as a funeral director.

When Joe and Heather work a sting operation involving an accused corporate raider they find out that he hired them to take a hit out on one of his fugitive co-workers. Meanwhile, Lily and Darnell pose as a book dealer's and a supplier in order to take down a forger who has been trying to pass off fake manuscripts as the real thing.

Joe must investigate Andy, a fellow FBI handler who's also one of his best friends, after a city councilwoman is murdered and the chief suspect is an informant under Andy's direction.

Joe and his crew pose as filmmakers involved in the adult-entertainment industry to lure a porn-obsessed man suspected of murdering his wife for insurance money. Also, an acquaintance asks Joe to help find her missing 14-year-old sister.

Joe and his team infiltrate a gang of thieves who plan to rob multiple jewelry exchanges across the United States.

Elena enters a rehab clinic in order to find out where $5 million in missing DEA money is located; Darnell poses as a hit man to thwart a murder attempt, in a case involving a nationwide drug ring.

Joe enlists the help of his former handler when two of his agents disappear during a dangerous mission. Also, Heather looks after a witness who thinks someone is following her.

Lily goes undercover as an Irish nanny in order to determine the whereabouts of another Irish nanny who has gone missing and is possibly dead. Joe tries to set Darnell up as a collector/enforcer for a high-powered bookie they want to bring down.

Agents go under cover to investigate the murder of a college intern who was romantically linked to a U.S. congressman. They learn they have the wrong suspect in mind.

Joe and his agents go undercover into the world of thoroughbred horse racing to take down a trainer suspected of murdering his horses.