BOOTH lies in bed with his ex-girlfriend REBECCA STINSON after they just finished what they both agree was a mistake. Booth's phone rings and Rebecca answers to BRENNAN on the other line. Booth takes the call and is out the door before you can say "awkward."
Booth meets Brennan at a construction site and she apologizes for interrupting him with her early morning call. Booth denies that he was doing anything scandalous with his ex. They enter one of the condominiums under construction and step into a crime scene. In the bathtub of an unfinished bathroom lays a deteriorated corpse floating in a chemical combination of household cleaning products. Brennan notes that the body has been submerged for two to three days and she decides to take the whole tub back to the lab.
At the lab with ZACK, HODGINS, CAM and ANGELA, Brennan reminds them that time is of the essence because the chemicals are literally eating their evidence. Cam demands that the identity of this body is the priority and Brennan believes that the priority should be solving why and how this person died. She reminds Cam that the ID of the body won't change, but the clues to what happened to it are vanishing fast. Cam stands down and confirms that the person weighed 165 pounds. She scoops the fat that has risen to the surface to measure its volume to determine body type.
Hodgins begins to separate the chemical from the organic and Zack pulls out a pitchfork to begin sifting through the tub. He fishes out a brittle femur bone connected to a hip replacement, the serial number chemically defaced. This suggests that the victim was elderly. In Cam's lab Booth arrives to find that Cam's determined that the victim was an ectomorph; thin, linear, narrow features. As Zack enters with a liquefied wallet, Cam asks Booth if he's back with his ex. Booth, caught off guard, denies it.
On the forensic platform, Booth confronts Brennan about spreading rumors about he and his ex. Brennan mostly ignores him as she studies the victim's bones under a microscope. She discovers that the victim was not elderly, but actually suffered from Osteogenesis Imperfecta, AKA Brittle Bone Disease.
Brennan takes this info to Angela and has her run a search on BBD cases in the area. She doesn't find any adult cases, but they're some children and the disease is hereditary. Brennan suggests they go talk to these kids and Booth suggests they do it separately. He didn't appreciate her gossiping behind his back.
Brennan arrives at the Seaver house to meet GAYLE SEAVER who tells Brennan that her husband, LARRY, has been on a work trip and out of contact for three days. Brennan thinks she's got a match and takes a picture from Gayle.
Returning to the lab, Booth boasts that he's found their victim. When he shows his picture to a confused Brennan, she holds up her picture for Booth. They both found the same man, but he's the father of two different families.
At the FBI offices, Brennan and Booth sit with LILA TURNER, the victim's other wife. She talks about how her husband was always going out of town on business, but she didn't mind because they couldn't get by on just her science teacher salary. Booth excuses Lila and sends her into an interrogation room set up to look like a waiting room. Then he sends in Gayle Seaver from Larry's other family. While Brennan and Booth observe the two women, Booth explains that he once loved his ex-girlfriend and that he has since moved on and that there is nothing going on. It appears as if they women in the waiting room have never met.
At the lab, Cam and Zack examine the victim's bones with Angela in the wings. Cam's found evidence of blunt force trauma to the skull and Zack confirms adding that it looks like a v-shaped weapon was used. He also found tiny copper shards at the bottom of the tub.
Back at the construction site, Booth informs the developer that Larry Seaver was the man they found in the tub. The secretary, CHLOE DANIELS, overhears this and is shocked, but the contractor, PETE VALERO, is furious because Larry owed him a lot of money through the development. He admits, he'd want him dead, but he didn't kill him.
At the lab Zack brings Cam a small stick of ivory that he found in the tub. He doesn't know what to make of it. She takes the ivory and tells Zack to head to the crime scene and look for weapon to match the blunt force mark found on the skull. As Zack exits Hodgins presents the finger of a rubber glove that he found under the stopper of the tub.
In Brennan's office, Booth shares that Larry had a $500,000 life insurance policy for the Seaver family and everything in his will was to be left to the Turner family. This gives the wives motive for murder. Cam enters and tells them about the glove finger. When she pulls a print off it, they'll have their killer.
At the FBI, Booth gets prints from both of Larry's wives and then reveals to them that they shared a husband. When it gets heated Booth gets a call from the FBI labs to inform him that the print from the glove doesn't match either wife. Booth escorts the women out of the office.
Just then, Rebecca, Booth's ex, arrives to find him, but she meets Brennan. Brennan asks what happened between them, but after Rebecca explains, Brennan tells her that Booth still has feelings for her.
Brennan joins Hodgins at the lab with an almost emptied tub. Booth hangs up his cell and tells the gang that the prints they pulled off the glove don't match anyone in the FBI database, which means it was a first time offender. Just as Hodgins begins to give Booth relationship advice, Zack enters with a junction box from the crime scene. The box had a hair embedded on it making either a weapon that was used or it was struck on a fall. Zack asks if they've found out where the copper bits he found came from and when Booth sees it he knows that it's birdshot, like shot gun pellets used on small game. Brennan concluded that perhaps Larry was shoot, blown back, and when he hit his head on the junction box his skull cracked because of the BBD.
Across the lab, Angela has confirmed that the stick of ivory is a chopstick used for styling hair. It must have fallen out of a women's hair when she was putting the body in the tub.
With Brennan and Booth en route, Booth explains that he remembered the contractor's secretary, Chloe, used chopsticks to keep her hair up. They head to a burger joint to find her and question her.
When they approach Chloe, with a tray a food that, Brennan sizes her up. Chloe thinks they're there for burgers and explains she's been eating burgers a lot lately for someone that considers herself a vegetarian. Brennan asks how long she's been pregnant, which takes Chloe by surprise. Brennan noticed by the way she was walking. Then, from around the corner appear Lila and Gayle with their children. Looks like somebody wasn't telling the truth earlier. Brennan takes a wild guess that Larry is the father of Chloe's baby. Chloe's face shows that she's right.
At the FBI, Brennan and Booth question the wives and Chloe. The wives explain that they met at a playground for special needs children because both of their kids had BBD and as they kept talking they put two and two together. To confirm their suspicions they followed Larry to work one day where he led them to a hotel where they discovered that Larry was cheating on both of them with Chloe, who says she didn't know he was married. Booth tells Chloe that they pulled her prints from the glove at the murder scene. When B&B say that the women must have been angry and confronted him together and killed him they explain that Larry was dead when they arrived, gun still in his mouth. They had told him why they were coming to meet him and he must have lost it. B&B exit. Booth's not buying it. There's no way that a man can shoot himself in the mouth and not drop the gun.
Rebecca arrives at the FBI to talk to Booth. She reminds him that he is a wonderful father and that they are better off not married. Booth agrees.
At the lab, Brennan has the gun used on Larry that she dug up from Gayle's backyard and confirms that it was in his mouth at one point, but then she asks Booth, what if he was shot after he was dead? This confuses Booth, so Brennan explains that the pits in his skull are void of blood, which means the birdshot hit after the blood stopped pumping. Cam arrives with new evidence. She's counted all the teeth found in the tub and came up with one extra, that is actually a crown and Booth remembers that the contractor had just been at the dentist getting a "root canal."
Booth and Brennan head to the construction site and cuff the contractor after Brennan confirms that he's got a matching molar crown. He admits inflicting the head wound and shooting him, but he still doesn't know how Larry got into the tub of lye.
At the lab, Hodgins and Angela share a moment discussing the case and the mental stability of the wives and Chloe. Sparks fly.
Brennan and Booth discuss Booth's love life and Booth explains that things between he and his ex are over and Brennan assures him that her gossiping days are over. Angela enters to stir the pot and tell Booth that Cam told her that Booth is back with his ex. Booth heatedly exits to Cam's office.
Later that night in Booth's apartment, we find him back in bed and the springs are squeaking. We find Booth, all smiles and by his side lay Cam. They both agree that this was a mistake, but a good one.