Season four begins all the way in England, with Booth speaking at Scotland Yard and Brennan guest-lecturing at the prestigious Oxford University. Knowing of Booth and Brennan's expertise in their respective fields, local officials ask for their help with a high-profile murder investigation that involves a British heiress.

With the case of the murdered heiress solved, Booth and Brennan prepare to head back home, but are shocked to learn of another murder - and this time it's someone they know. Meanwhile, with Birimbau unexpectedly coming back into Angela's life, things get complicated between her and Hodgins.

The body of the host of a popular reality TV show is found partially decomposed in an outhouse, and Booth and Brennan must find out who the killer is. Meanwhile, Booth learns that Brennan is juggling two relationships.

Parker, Booth's son, discovers a corpse's finger in a bird's nest, causing the team to launch an investigation to try to find the rest of the body. After finding the corpse, the team discovers that the death was caused by a dog, leading them to an illegal dog fighting ring and a search for the killer dog and its owner.

The pieces of a dismembered body are found lying in a purple pool of water, except the head is missing. The team finds that the body belongs to Jared Addison, a science fiction writer who had several mental problems. With Sweets' help, several suspects are hunted down, however the team has trouble finding enough evidence with the victim's head still missing.

The remains of a despised office manager are discovered in an elevator shaft, and Booth and Brennan must figure out which employee killed him. After some investigating, they find that the manager had more than a fair share of complaints on file. Meanwhile, Angela and Hodgins try to make peace in the lab after their break-up.

Booth and Brennan go to investigate a body found in the Chesapeake Bay. After arriving, they find only the upper torso, giving the team little to work with other than remnants of the victim's breast implants. Brennan and Booth are led to a small church in Maryland, where they find that the victim was a pastor. When the team finds the lower half of the body, they learn that their initial assumptions may not been incorrect.

When the smashed remains of a well known artist are found in an impounded junkyard car, Booth and Brennan are on the case to find out if foul play is to blame for his death. With suspects ranging from the artist’s rival to his own assistant, the team must race

against the clock to find evidence of murder before the car is relinquished and put on exhibit as the sculptor’s ultimate display of self-sacrifice for the sake of his art.

Booth’s Brother Jared Booth and Brennan investigate the scene where a body was uncovered during a botched practice police raid. The team identifies the body as a struggling inventor’s father who had recently reunited with his son. But when a second body surfaces, the team is led on a trail of deception to find out who was the actual con-man in the inventor’s life. Clark Edison returns to the lab, and he and Hodgins work on piecing together blueprints from one of the inventor’s potentially valuable inventions.

Meanwhile, Brennan likes Booth's brother and goes out on a date with him. She learns a thing or too about Booth's past while out on the date.

While en route to China to identify prehistoric anthropological remains, Booth and Brennan are called upon to solve a murder in midair when the flight attendant discovers a fully cooked human body in the plane's microwave.

Brennan's father Max lands a teaching position at the Jeffersonian. When he ends up helping out with the murder case at hand, Brennan is noticeably bothered by his sudden presence in her professional life.

A shallow grave holds the remains of conjoined twins; Booth and Brennan infiltrate a circus community after they discover that the twins were jugglers there.

When a volunteer fireman is murdered at an ice rink, Booth and Brennan begin the investigation, but Booth must excuse himself due to a conflict of interest. When details come to light, Booth becomes a suspect in the homicide.

While trapped and trying to escape from a ship in the middle of the ocean, Booth is haunted by strange hallucinations.

The team investigates a sci-fi convention when a woman in a medieval princess dress is found murdered. With Booth's back injured, Agent Payton Perotta steps in once again to help

When newlyweds encounter a corpse while bungee-jumping off of a bridge, Brennan and Booth are sent to investigate. After determine the cause of death was not suicide, the team at the Jeffersonian discover an unknown substance coming from the body. This sends the lab into lockdown and have only 24 hours to uncover the murderer before the body disintegrates.

The body of a pregnant 16-year-old athlete found buried in a mound of salt in a city de-icing truck leads Booth and Brennan to the discovery that many of her teammates are pregnant or have babies after a pregnancy pact.

When the half-eaten body of Cam's former fiancee is found in the tiger cage at the zoo, Booth and Brennan uncover that his death was far from accidental. Now the team must put the pieces of the fiancee's final day back together, including hypnotizing a suspect in order to spark his memory.

Booth and Brennan are sent to investigate when human remains are found during a photo shoot. When the team uncovers a meteorite in the victim's ear, they are led to the Collar Institute of Science in D.C.

Booth and Brennan are called when an image of the Virgin Mary is found in a bale of compressed cardboard.

When it is discovered that a stage prop used by a Norwegian death metal band is in fact a real human skeleton, the remains are sent to the Jeffersonian when authorities determine the victim was an American citizen.

When a Jeffersonian coworker dies of heart failure, the entire team goes to the wake where, upon viewing the body, Brennan realizes the death was no accident.

Booth's detective friend from Tokyo, Ken Nakamura, calls him when his sister, Sachi, goes missing while in Washington, D.C. With Brennan, Booth investigates her disappearance.

When a human body is found inside the strung up Otter mascot uniform of a rival school, Brennan and Booth investigate whether the body inside the costume was dead beforehand, or killed during a Middlesex University bonfire event. The body is identified as Jimmy “Beaver” Bouvier, a fraternity brother at Middlesex University. When Brennan and Booth question his fraternity brothers, they learn that Beaver had a money-making operation on the side and was making a killing of his own. Meanwhile, Booth offers to help his brother Jared find a new job after being dishonorably discharged from the Navy.

The team is on the case when human remains are found inside a barrel of wine during a wine tasting. When the victim turns out to be a wine critic whose scathing reviews were capable of sending a vineyard to its ruin, everyone from the winery's owner to the victim's own wife becomes a suspect.

In the season finale, a dead body is found at a club called "The Lab." The team has to do some unexpected and unusual things that have to do with this club. Brennan and Booth may become a couple.

It's been six weeks since Booth and Brennan have seen each other. Booth has been recovering from brain surgery, and Brennan has been on a dig in Guatemala. Angela's psychic, Avalon Harmonia reveals while reading Angela's tarot cards that there are multiple bodies buried under a Washington,DC fountain. Angela shares the information with Brennan and Booth, but they're both a little skeptical. The lead pans out, and the duo find the remains of 11 bodies exactly where the psychic said they would be. Meanwhile, Sweets has certified Booth mentally fit to return to duty after his brain surgery, but Booth is still experiencing some side effects from the coma.

Brennan and Booth are asked to investigate the death of a man who was murdered for the secret contents of his briefcase. They suspect that secret operatives are at work, and their theory is proven correct when they find the liquefied remains of a CIA agent in the trunk of a car. Meanwhile, Brennan's new best-selling book causes tension between her and Booth, and Wendell loses his scholarship.

When human remains are found alongside the railroad, Brennan and Booth are called to the case. The bones belong to Levi Yoder, a member of the Amish community who disappeared two months ago, during his Rumspringa, or exploration of the outside world. Brennan and Booth discover that Levi was a piano prodigy, and their investigation leads them to believe that his extraordinary talent may have lead him to an untimely death. Meanwhile, Cam copes with the stress that comes from being a new parent.

Brennan and Booth investigate human remains found at a neighborhood block party. Suburban politics and secret scandals give each neighbor in the cul-de-sac a motive, leaving Brennan, Booth and Sweets to sift through the drama to find their suspect. Meanwhile, Jeffersonian intern Arastoo comes clean about his background, and Booth's son attempts to find Booth a girlfriend.

Brennan and Booth are called to investigate what appears to be charred human remains on an electrical fence. The mysterious corpse is later determined to be a mummified Egyptian royal on loan to the Jeffersonian. The anthropological mystery has Brennan in a tizzy, and when the Jeffersonian curator prepping the mummy for exhibition is murdered, the team suspects foul play. Brennan’s investigation of the curator sheds new light on the life of the Egyptian royal, turning their case into one of historic proportions. Meanwhile, Brennan goes on a date with Booth’s supervisor and former intern, and Sweets’ girlfriend Daisy Wick (guest star Gallo) returns to the Jeffersonian.

Remains of a chicken farmer are found on the bank of a nearby river, and Booth and Brennan are called in to investigate. The farmer, who was an animal rights activist, was about to inherit a chicken factory and had many enemies with motive to kill him – leaving the team with a lot of murder suspects to sort through.

Stephen Fry returns as Dr. Gordon Wyatt. Booth, still suffering some lingering effects from his brain surgery, has to get re-certified for FBI marksmanship, but is not the accurate shot he was before going under the knife. He and Brennan investigate the death of a little person who was a former wrestling star.

Booth’s grandfather comes to live with him and tags along as Brennan and Booth investigate human remains that were found by a real estate agent while showing a property to prospective buyers.

When the remains of a competitive gamer are discovered in a grease truck, Brennan and Booth are called to investigate the case. The victim, Steve Rifton, is the only active player known in the gaming community to have received a perfect score on a famous video game. Steve turned his success into a lucrative partnership with a gaming referee and charged fans to play on the very machine that gave him the perfect score. But between sour business deals and bitter competitors, the team at the Jeffersonian must work to narrow down the many suspects with motive for ending Rifton’s reign as gaming king. Meanwhile, Hodgins, Sweets and Jeffersonian intern Colin Fischer take turns camping out for tickets to a movie premiere.

When a man dressed as Santa Claus blows himself up during a botched bank robbery, Brennan and Booth work to identify the bomber and determine his motives. Meanwhile, Brennan makes plans to spend Christmas in El Salvador, but her father convinces her to spend the holidays with him and Margaret Whitesell, a newly discovered distant relative.

Brennan and Booth travel to New Mexico to investigate human remains with extraterrestrial attributes. Meanwhile, Angela and intern Wendell come clean about their relationship.

Mr. White and his team of government agents put the Jeffersonian Lab on lock down and demand that Brennan and her forensics team determine a cause of death for an unidentified, but highly classified set of remains. As the team gets to work, their findings lead them to suspect they are investigating one of the most famous presidential assassinations in history. Meanwhile, Booth's boss, Andrew Hacker, helps him break into the lab and determine the motive behind the mystery investigation, and a frustrated Cam worries that Michelle may be keeping a big secret from her.

When a human skeleton is discovered in the trenches of an old Civil War battleground, Brennan and Booth are called to the case. Despite the historical location, Brennan quickly identifies the bones as belonging to Dan Pinard, a present-day local dentist. While Booth investigates suspects, including the victim’s former boyfriend, Hodgins and lab intern Vincent Nigel-Murray work doggedly to clean the bones of a stubborn clay residue which is preventing the team from determining a cause of death. Meanwhile, Booth’s brother, Jared, returns from his travels with some suprising news.

Brennan and Booth investigate a set of uniquely disfigured remains allegorizing biblical text. As they acquire more information about the victim, a former patient of Dr. Adam Copeland at Havenhurst Sanitarium, they are confronted with suspects who are hard to characterize as either good or evil. Meanwhile, Jeffersonian intern Arastoo Vaziri reveals a secret about his past.

When a subway train is thrown off the track by 60,000 gallons of flood water, a partially skeletonized body emerges out of the overflow. While Dr. Sweets, a passenger on the derailed train, copes with post traumatic stress, the rest of the team and intern Daisy Wick get to work on identifying the victim as Martin Aragon, a professional ghost writer caught up in a deadly love triangle. Meanwhile, Brennan releases her second book to great success, but has to accommodate a nosy reporter, and Sweets' near-death experience leads him to make a drastic decision.

When Dr. Sweets' book gets published, both Booth and Brennan read it and tell him about the first time they met: 6 years ago. The episode will give a new perspective on Booth and Brennan's relationship, and will also give viewers the chance to see Zack Addy again, and Dr Saroyan as a New York Coroner.

The team’s latest case takes Brennan back to her alma mater, Burtonsville High School, where she and Booth investigate the discovery of an unidentified skull and upper torso. With Angela’s help, they identify the victim as one of Brennan’s classmates, and notice a possible connection to a second murder committed 15 years prior. Brennan and Booth go undercover as a married couple at her class reunion to interrogate a set of suspects, where even as an adult, Brennan is still predictably misunderstood and her only friend lies in a strangely dark and offbeat janitor. Meanwhile, Hodgins spills a lab secret

When human remains are discovered in the belly of a shark, Brennan and Booth are brought in to identify the missing person. Evidence suggesting the victim had been the prey of several fish directs the team’s investigation to The Aquarium of the Atlantic, where a guest lecturer and notorious self-help guru preaching the healing power of the ocean has gone missing. Meanwhile, both Brennan and Booth navigate their own relationship when a marine biologist shows interest in Booth.

Booth and Brennan investigate a death at a rock-n-roll fantasy camp where the murder weapon is a Gibson ‘57 Les Paul “Black Beauty.”

A cabin burns down in the woods revealing two bodies, one of a modern-day witch and one from the days of the Salem Witch Trials leading Booth and Brennan into the world of Wicca to find a killer. Meanwhile, when Hodgins' reckless driving gets him and Angela arrested and thrown in jail, Sweets and intern Clark Edison step into unfamiliar territory to help out the team

The trial of The Gravedigger hits close to home for members of the team, and everyone at the Jeffersonian must work overtime to uncover the forensic evidence to elicit a conviction.

The team works to uncover clues buried under a life’s worth of possessions saved by a hoarder in order to solve the mystery of his death. Meanwhile, Angela’s father has a specific purpose for his most recent visit, and Brennan and Booth are confronted with unique opportunities.