After a skull smashes into the windshield of a teenager's car, the investigation reveals the skull has been gnawed on by human teeth, which implies cannibalism and marks the beginning of the Widow's Son case. Meanwhile, Angela and Hodgins hire a private investigator to find her husband. Bones searches for Zach's replacement and the team gets a wonderful surprise.

Brennan and Booth investigate the death of a soccer mom who was blown up in her mini-van. They soon discover that the victim was part of a group of radicals from the 70's, adding several names to the list of possible suspects.

Things get kinky when Booth and Brennan follow murder clues that lead to a lodge used as an S&M retreat for "jockeys" and their "horses." Meanwhile, Angela tries hypnosis in an effort to figure out her elusive husband's name so she can finally divorce him.

When a body that appears to be cooked is discovered, the clues lead Booth and Bones to an organic farm co-op. Meanwhile, the two of them must meet with Lance Sweets, an FBI psychologist who must determine if they should continue to work together.

On Halloween, two mummified bodies are discovered and found to be people reported missing the past two Halloweens. When Booth and Bones learn about a missing girl, linked to the suspect of the previous murders, the race is on to save her life.

The team suspect their own colleagues after the burnt remains of an intern at the Jeffersonian are discovered. Meanwhile, Booth poses as Cam's boyfriend at her family get-together.

On the 20th anniversary, the Foothill High School, class of '87 alumni unearth the time capsule they buried to discover the remains of one of their classmates inside. Booth and Bones investigate the past lives of his classmates in an effort to discover the truth.

After the body of an archbishop is found, missing the kneecaps, the team concludes the murder is related to the Widow's Son case.

Booth and Brennan investigate a mall Santa named Kris Kringle who was found dead by two elves. A series of clues makes the murdered mall Santa seem like he's the real deal.

A body discovered in a hot spring turns out to be that of Tripp Goddard, a sexy motorcycle racer who had disappeared two weeks earlier. Sweets talks Booth and Bones into going out with him and his girlfriend.

All team members are working to identify the bones from a college athlete who suffered a lot of fractures. After the body is identified they talk to his sister and somebody who acted as a sort of an adviser for the deceased. Angela and Hodgins have an important talk. Zack is overwhelmed by having to reconstruct the crushed bones to form a skeleton.

A woman's car is run off the road and she is killed, but her baby miraculously survives the accident. Booth and Brennan go to the woman's hometown to try to find out who's responsible for running her car off the road. Bones, with help from Booth, takes care of the baby until the team finds out who killed the mother.

Brennan's father Max Keenan is on trial for the alleged murder of FBI Deputy Director Kirby. Everyone on the team, except for Brennan, is called as a witness for the prosecution during the trial. Brennan on the other hand is the forensics advisor for the defense, and she must rely on both her dedication to her family and her skill as an anthropologist to help free her father.

A wannabe singer Tommy Sour was found on a grassy location. The investigation leads Brennan, Booth, and Cam to the Checker Box Restaurant where Tommy used to sing. There are several suspects who took part in the open mike contest there, with talent scouts in the audience. The group comes together with a startling revelation for Brennan.

The Gormogon serial killer is back again, and the silver skeleton from the basement vault has gone missing. All the Jeffersonian employees become suspects, with the scary possibility that one of their own is working with Gormogon.

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.