After Charlie and Amita get married and begin preparations for their London adventure, they put a slight hold on their wedded bliss when they assist the team in helping Don track down the whereabouts of his gun after it goes missing.

Feeling guilty over the stabbing, Charlie puts his attention on finding a serial killer using math theories to help the team solve the case before another life is taken.

Don's life hangs in the balance after he is injured during a raid while investigating a series of home invasions.

The city is in a panic as a sniper goes on a shooting spree and randomly kills several people, including a postal worker. The investigation reveals that more than one shooter is at work. As Charlie works the case, he's frustrated by a sniper expert Don brings in to help out.

The team investigates a decommissioned air base after a woman is found dead there, but their investigation is interrupted by paranormal happenings.

In the midst of investigating a serious bomb threat, Don and Charlie uncover a secret that could change their lives and the lives of the team forever.

When an assailant opens fire in the FBI offices, Don and his team must determine his motive and possible connection to a dangerous arms dealer who is on trial. After nearly getting shot, Charlie is shaken and reluctant to return to the offices, which hinders his contribution to the case.

David tries to get information from one of Crystal's old boyfriends, but he isn't helping. Things get personal for the team when Crystal kidnaps one of them.

In the season finale, Don and Charlie work together on a case that ends up with them going head to head about their personal beliefs, and one team member will walk away forever.

While consulting with the NTSB at the scene of the wreck, Don learns that this tragedy is one of a series of recreated accidents involving railroad negligence. As is the pattern with the previous train wrecks, an undecipherable numerical code is left at the site, which Don recruits Charlie to solve. By breaking the code, Charlie is able to establish that this accident was a recreation of a deadly wreck that left only one survivor several years ago. Don's investigation leads him and his team to a dangerous standoff with their suspect, who has surprising ties to the railway system.

To help capture a serial rapist-turned-killer, FBI Special Agent Don Eppes recruits his genius brother Charlie, who uses a mathematical equation to identify the killer's point of origin by working back from the crime scene locations.

Don talks to his therapist again, and while he's gone, the team races to find an eleven year-old boy being held on a $3 million ransom, and time is running out...

The Numbers team hunts for a gang of criminals who targeted an unlikely scene of the crime: a televised entertainment awards show.

After the events of "The Janus List," Colby escapes from custody. Don and the team go after him, but everything may not be as it seems.

When Don and his team are called to the scene of the murder of a Los Angeles gang member, they learn they are investigating the murder of another agent who had been working undercover.

While tracking down a felon running a heroin ring inside a prison, Agent Ian Edgerton becomes a murder suspect when the informant he meets with ends up dead, sending a desperate Edgerton over the edge when he takes a member of Don's team hostage.

Various people in the L.A. area with seemingly nothing in common start to become extremely sick and die on the same day. Don fears bioterrorists may have released a deadly virus into the environment. While he tries to discover whether anyone is behind the outbreak, Charlie tries to locate the point of origin.

Don has a problem. Crystal Hoyle and her boyfriend Buck are going on a robbery and killing spree. Their terror is spread over seven states, and Charlie is called in to help. However, problems between Alan and Charlie may hinder Charlie's concentration.

Charlie and Don reluctantly enlist the help of imprisoned con man John Buckley to help them catch a crook who's using Buckley's M.O. to rob the Diamond Exchange..

When Amita is abducted, Don and the team’s frantic search for her leads them to the delusional head of a cult, but it is up to a distraught Charlie to discover what the suspect’s bizarre plans for her are.

After four people nearly die from poisoning, Don learns someone is tampering with nonprescription drugs. When the perpetrator publishes a manifesto in a local paper, Don is led to believe the person may be a former employee of the drug company that manufactured the drug.

Don and his team must race to save the hostages being held on a hijacked bus.

Don learns that counterfeiters are at work producing small-denomination bills, and that they have taken an artist hostage to draw the images for the fake money. If the missing woman isn't located soon, Don fears that she will be killed when her work is finished on the phony cash. The counterfeiters have already murdered at least five people, two of whom stole money from them. The case is made more difficult for Don when his former lover, now a Secret Service agent, is assigned to it.

A man wanted for stock fraud is found garroted in his apartment, and the crime is eerily similar to a murder committed a year earlier, a case in which Don closed when an ex-con confessed. Now, Don must re-investigate the old case to determine if he put an innocent man in jail. He asks Charlie to go over the evidence to see if he missed anything the first time around.

Megan feels responsible for an agent's death following an explosion at a meth house the FBI had targeted for a bust. When the kingpin eludes capture, it's discovered he may also be involved in child pornography when one of the photographs on his computer turns out to be a young girl in a sexually explicit position. The picture sends Charlie on a crusade of his own, as he remembers a girl he knew as a young child that he suspected was being abused, and he's determined to save the little girl in the picture.

When a former mob hit man on death row suddenly has a change of heart and agrees to confess to his crimes, Don has an uneasy feeling about the whole affair.

When the team foils a robbery of an armored car full of Federal Reserve money and recover bills that trace back to the infamous D.B. Cooper heist, they call on Agent Roger Bloom, who worked on the Cooper case, for help with the investigation. Henry Winkler returns as former FBI Agent Roger Bloom, and Michael Hogan, the uncle of the slain armored car driver and a key player in the investigation.

$50 million dollars in medical relief is up for grabs after the shipment is stolen. But there's a catch--someone other than the FBI wants to recover the shipment. Don and the team find themselves pitted against blackmarketeers in a deadly race for the supplies.

After an engineering student at CalSci is found dead from an apparent suicide, Charlie convinces Don to launch an investigation after he reads the student's thesis that asserted that the architecturally magnificent Cole Center in Los Angeles is structurally unstable. Although reluctant at first, Don and his FBI agents discover that the student's findings were correct and uncover a dangerous and surprising conspiracy. Meanwhile, Alan prepares for a first date and convinces Don and Terry to join them, hoping they might rekindle their old romance.

When a five-year-old girl is kidnapped from her birthday party, Don and Terry lead the investigation, but must rely on Charlie's help because the girl's father, Ethan, is also a mathematician. Charlie realizes the kidnapper's motive when Ethan reveals he is close to solving Riemann's Hypothesis, a difficult math problem. If solved, the solution could not only earn him $1 million, but could break the code for internet security and unlock the world's biggest financial secret.

An FBI investigation into a computer hacking scam that taps into a bank's system to gain access to the identities and financial assets of its customers becomes personal for Don and the Eppes family.

A dangerous felon escapes when a prison bus crashes and the FBI has reason to fear he's intent on revenge against the witness whose testimony put him in jail. However, finding the elusive killer proves to be a complicated challenge. Don teams up with Agent Billy Cooper, his former partner from the FBI's Fugitive Recovery Division, and Alan worries that Don's going to return to a more dark and obsessive time in his career.

Charlie meets his mathematical equivalent when lottery agent Jane assists in the investigation into a complex scam that involves thefts of unsold lottery tickets.

Don and Megan are called to the murder scene when the CFO of a powerful energy company - who was about to testify against her fellow executives - is murdered at her home and her son is the only witness. Knowing there could be thousands of disgruntled ex-employees, Don asks Charlie to narrow the list.

When a passenger train collides with a freight train David (Alimi Ballard), Don, and Colby are called in to help rescue survivors and to investigate the cause of the crash

The team gets a last minute tip that could exonerate a dangerous mob boss who is about to be executed; Charlie tries to help the CalSci basketball team break their losing streak.

When a wealthy heiress is kidnapped, Don and the team race against the clock in hopes to find her. However, the motivations behind her disappearance aren't what they seem.

Don feels responsible for a life lost. The victim was in the Witness Protection Program, but she wasn't the only one keeping secrets...what is Don hiding?

When a car crashes into a busy coffee shop, the team discovers the fatal act might not have been an accident.

Charlie's life is put in danger when Don brings him in on the case of a missing reporter.

A feud between Chinese gangs leads to the kidnapping of an undercover agent and the reappearance of Samuel Kraft.

Don, Charlie, and the team search for a polygamist who is on the run. The man is on the FBI's Ten Most Wanted List for rape and murder.

An actor on his way to stardom finds himself in the middle of a murder investigation when a young woman is murdered in his house.

Don, Charlie, and the team attempt to stop a serial killer who is seemingly obsessed with people resembling Biblical figures.

The team searches for a pair of limited edition sneakers after they are stolen from a foreign ambassador.

Don turns to his newly found religious beliefs when he is forced to deal with an escaped criminal who is bent on seeking revenge.

Don and his agents are asked to investigate when a search team finds three dead women in the wilderness who were apparently murdered under bizarre circumstances. The case becomes more suspicious when Don learns the search team was led to the crime scene by a psychic. When the psychic offers to help the FBI in solving the crime, Charlie is determined to prove the psychic is a fraud.

When a researcher who specializes in Native American antiquities is killed at the museum where she works, the FBI is called in because the museum is on federal land.

Charlie is forced to turn to his arch rival for help when a vigilante group goes after a career criminal.

Don and the team must investigate a religious cult after scores of followers are poisoned.

When two police officers are killed while eating dinner out, Charlie tries to figure out where the killers will strike next. Don's superiors make him see the department shrink.

Don and his team are called in to investigate who is behind a deadly gambling ring that is running a high-stakes Russian roulette tournament. Also, Don and Charlie become concerned about Alan's financial health.

Don and the team investigate when a magician mysteriously vanishes during an illusion.

After an extremely expensive yacht sinks in the middle of a race, Charlie is put between a rock and a hard place when Don and the NSA need his help on the case.

The problem of the disposal of toxic waste becomes real to Don, Charlie and the team when several children are injured after a sinkhole collapses underneath a school playground. Charlie attempts to help with the case, but faces opposition from his new boss.

Don and the team reopen a cold case when a LAPD badge turns up at a construction site. When Charlie joins the investigation, they attempt to track down the owner of the badge, an officer who has been missing 17 years. Meanwhile, Alan is informed that he's being sued.

Robberies the storybook hero would have been proud to claim plague Don and Charlie as they attempt to catch a do-good thief who is donating his spoils to charity.

Don and Charlie investigate the murder of a judge's wife who was shot in her garage. It's unclear whether she was the intended target or her husband, who was hearing a death penalty case involving a gang leader. As the investigation continues, Don reconnects with a prosecutor whose life may also be in danger.

Don runs into Robin Brooks during an investigation concerning informants and a chess master.

One of David's closest friends is called into question after a man dies while boxing with him. When it turns out this is not the first time such an event has happened, things look even worse. Charlie is busy practicing what little he knows about poker, so he can take Larry's spot in a tournament.

The gang uses their math--and a reluctant gun merchant named Randall P. -- to track down a missing shipment of new, deadly but defective assault weapons which are hidden among the thousands of containers in one of L.A.'s busiest ports.

When a musician is murdered, Don and his team must race to find the culprits. They need Charlie's help, but he is busy with Amita's parents coming for a visit.

Don and the team bust a meth lab, but when Don has a feeling there's more to the organization than just what's on the surface, his intuition is put to the test.

One of Don and Charlie's friends dies in what is deemed an accident. Not convinced, the brothers investigate further and uncover something shocking.

Two rock climbers in possession of a large stolen diamond are killed, and Don and the team hunt for the murderers; Charlie considers whether he should have his FBI clearance reinstated.

The FBI becomes involved in the stalking of a popular singer after she is threatened by an intruder in her house and reveals a series of threatening letters she's received through the mail. Charlie determines the letters are from two different people after analyzing the handwriting. When a photographer is found dead near the singer's house, Don believes the photographer was murdered and his death is somehow related to the stalking case.

Don and his team investigate a school shooting. He learns two students could have a strong motive, so Charlie uses the school's radio frequency identification system to track the shooters' movements through the school's hallways. When Charlie detects an abnormal pattern, the agents take a look at the evidence and discover a third participant no one had suspected earlier.

The team investigates the theft of a graphic comic book.

Don, Charlie, and the team take on unknown terrorists who may be using nerve gas to undermine Los Angeles' water supply.

Don and his team hunt for an ex-Marine wanted for murder. Things become confusing, however, when the Marine's family is kidnapped. Is there more to this case than meets the eye?