Heather Taffet aka The Gravedigger was a serial killer who buried people alive and held them for ransom.
Not much is revealed about Taffet's life prior to becoming the Gravedigger, but it was revealed in The Hero in the Hold that she, in 1998, was married to a man named William Burton for exactly one month before having the marriage annulled. She used that brief marriage to create an untraceable fake identity she used to rent a storage facility where she stored her kidnapping equipment.
In her first appearance in Aliens in a Spaceship, the Gravedigger (who at the time was believed to be a man) has performed six abductions. The victims of four of them were released when the ransom was paid, but the family of one victim, Terrance Gilroy, didn't pay and the body was never found (though the Gravedigger strangled him almost to death before burying him), and a sixth case, Ryan and Matthew Kent, failed for both her and the boys' family; the Gravedigger had intended to kidnap one of them, but ended up abducting both. When they were inside the container, which held enough oxygen for 24 hours, they used it twice as fast and they died; despite one of them killing himself in order to give the other more time. A Kidnapping and Ransom expert, Thomas Vega, felt that the FBI's policy not to pay ransoms was antiquated and dangerous and, in collaboration with a journalist, wrote Uncovering the Gravedigger. The seventh abduction has the team racing to find the victims, Brennan and Hodgins, before time runs out.
Season Two: Aliens in a Spaceship
All the surviving victims were the ones whose families or relatives paid the ransom, until The Grave Digger abducted Temperance Brennan and Jack Hodgins. Brennan had delved too deep into the case and Hodgins was also abducted because he ran out to tell her something important and interrupted the kidnapping. The Grave Digger buried both of them in a car and requested an $8 million ransom. This was unusually higher than the previous requests and most likely different because Hodgins is the sole heir of the Cantilever Group, the third biggest privately owned company in the United States. The Group were unwilling to pay the ransom with no proof of life, but thanks to Brennan and Hodgins managing to use the car battery to temporarily 'jump-start' Brennan's phone and send a coded text to Seeley Booth, they were able to provide the team with a vital clue to work out where they were being held before air ran out.
Season Four: The Hero in the Hold
The identity of the Grave Digger is revealed to be Heather Taffet. She is a United States attorney who took over the Gravedigger case after the last attorney assigned to it, Kim Kurland, was killed in a car crash. It is surmised that Taffet killed Kurland by somehow sabotaging her car; Taffet does this to gain complete access to the Gravedigger case, to steer the case away from her, and eliminate people who she sees as threats. She kills Thomas Vega when he begins to dig further into the case and abducts Booth to force Brennan and Hodgins to return a key piece of evidence so that she can destroy it.
She was identified as the Gravedigger when Brennan surmises that a fracture on Thomas Vega was caused by a defensive wound which would have given the attacker a broken rib. When Taffet was handing over some documents to the group, Temperance notices that Taffet could not lift her arm proficiently and after a careful strike in the right area reveals to everyone the Gravedigger's true identity. She remains silent to the team's attempts to interrogate her for information on Booth's location, until Jared Booth uses his military contacts to go through Taffet's background, this technically illegal search allowing them to find the equipment she uses as the Gravedigger and the abandoned ship where she had left Booth.
Season Five: The Boy with the Answer
She represents herself in court after being indicted and the evidence that was found in a storage locker is disallowed as illegally obtained. She hints to Bones about not finding "the number" yet (meaning a phone number), which ends up being the number she called when she was in jail. The number initially led to a pizza place, until Angela figured out that they were the coordinates to where one of her victims, 10 year old Terrance Gilroy, was buried. Although Taffet had intended for the discovery of the boy to be a taunt to the team, Bones and Booth use the evidence in that murder to convict her, forensic examination of the body confirming that he was killed by someone with Taffet's physical characteristics and a DNA sample acquired from the boy's mouth confirming that he had bitten Taffet as she attempted to kill him.
Season Six: The Bullet in the Brain
When Taffet appealed her conviction, she was on her way from prison to the Federal Courthouse to participate in her appeal when she was killed by a single rifle shot to the head. The power of the .338 Lapua Magnum completely destroyed her head and skull, spraying blood and brain matter all over the place, some of which landed on Lance Sweets who Taffet had been taunting and mocking just a few seconds before her death. The subsequent investigation revealed that she was killed by Jacob Broadsky, Booth's former mentor, who had approached James Kent, the father of Taffet's old victims Ryan and Matthew Kent, and offered to kill her for the sum of $2 million (This was the amount which Taffet had demanded as ransom for the two boys; presumably, this was an act of revenge on Kent's part as he sought to avenge the death of his two sons).
Taffet abducted her victims inside parking garages from spots where security cameras couldn't see them, stunning them with a modified stun gun, and running over any witnesses (such as in the cases of the Kent brothers buried, and with Brennan and Hodgins being buried. The grave-digger only planned on burying one) and burying them alive inside some kind of container large enough to house 24 hours of oxygen. She then makes a single phone call to a friend or family member of the victim with a ransom demand for some millions of dollars (the amount depends on how much the family of the victim can afford) using a digitally altered voice. As forensic counter-measures, she used containers which couldn't be traced back to her such as the victims' own cars, coffins, rusty refrigerators, or beer vats, and used untraceable foreign bank accounts for collecting the ransom money.
- September 1999: Terrance Gilroy (strangled; his family didn't pay the ransom)
- Unspecified dates from 2000 to 2005: Four unnamed victims (all were abducted and rescued when their families paid the ransom)
- October 31, 2001: The Kent brothers (both abducted and died)
- November 14-15, 2006: Temperance Brennan and Jack Hodgins (abducted; were rescued)
- Sometime in 2008: Kim Kurland (sabotaged car)
- February 4-5, 2009: Seeley Booth (abducted; was rescued)
- February 4-5, 2009: Thomas Vega (heart stopped from stun gun to chest)
- Because of her intellectual acumen, cold nature and complete lack of morals Heather Taffet could be considered the Anti-Brennan. While Temperance Brennan isn't overly emotional, she displays affection to those closest to her, albeit with slight awkwardness. While Brennan doesn't always understand conventions or certain rules she does adhere to them. While Brennan dedicates her exceptional level of intelligence to finding and catching killers, Taffet chooses to use her intelligence and knowledge of the criminal justice system to keep herself hidden, take advantage of people considered beneath her, and even throw out non-negotiable ultimatums at her enemies in an attempt to keep herself from getting arrested and/or sent to death row for her crimes.
- The Fox Network website initially displayed a summary for the episode which included an original ending where the Gravedigger was identified as Janine O'Connell, the female reporter that coauthored a book about Gravedigger and scenes to this effect were filmed. The summary was later revised to reflect the episode as broadcast in which the Gravedigger is unidentified and the scene replaced by character reunion moments.
- The M.O. and mistakes of the Gravedigger appear to be derived from the kidnapping and murder of Ursula Herrmann, a German girl imprisoned in a box for ransom and dying from suffocation and malnutrition within hours. The M.O. also appears to relate to Barbara Mackle, who was forced out of her home after her family was bound in their house, with two kidnappers keeping her in a box and demanding two ransom drops for her return.