In the Southern Highlands, on a hillside at night, a man kneels beside a metal case. He reaches in and begins to assemble several metal tubes that form a barrel, which he mounts on a tripod, and attaches a scope. He peers through the eyepiece and focuses on a man in a house in the distance. Then he tilts his scope up and looks at the stars.
He adjusts his telescope for the light pollution that seeps in his scope. Orange light invades his field of vision and then he sniffs the air before looking up to see a fireball rolling down the hillside, igniting everything in its path. He screams as he runs away, but the fire washes over him. Investigator Chief Rick Dysart is on the scene with the CSIs. He tells them that a local homeowner called in the fire. The stargazer is dead, completely burned. Grissom notices that there are "optimum conditions" for arson, with the low humidity and plenty of dry brush. Dysart informs them that the fires started at the top of the ridge and spread down.
Grissom finds a charred body, barely recognizable as female, lying by a tree. Suddenly the woman's eyes snap open. Grissom shouts for emergency help. Greg Sanders is in the burn unit of a hospital, observing as a team works on the horribly burned body of the victim. Dr. Franks tells him, "This is as bad as it gets." Greg says he will need her clothes as well as any trace off of her body. Dr. Franks tells him he will give him whatever he finds during debridement, when they scrape off the dead flesh and cover her with cadaver skin in order to avoid infection. Greg watches them cut off her wedding ring.
Catherine and Warrick are at a suburban house talking to Captain Brass as they watch a 5-year-old girl being carried away on a gurney. The child, Dani Stewart, drowned and the neighbors saw her floating face down in the pool. Her parents were inside the home.
Catherine and Warrick enter the dark house and find a cascade of blood dripping from the staircase into an indoor water fountain. Their maglite's beam finds the source--Corinne Stewart, 29, lies on the steps, a single gunshot wound in her back.
The CSIs enter the master bedroom and find the dead body of Morgan Stewart, 32, who lies diagonally across the bed, head hanging off the edge, a pool of blood soaking the carpet below. The handgun he holds in his right hand appears to have been wiped clean. They speculate a professional killing of the parents and the little girl was a "loose end."
In the daytime, Sara and Grissom are looking over the charred hillside, trying to find clues. Sara finds the top of a cheap, butane lighter. Grissom comes across a broken bottle of cheap vodka and quips, "Did you know the word 'vodka' comes from the Russian word, zhizennia voda, 'water of life?'"
David Phillips enters the Stewart house and finds Nick and Catherine processing the master bedroom, setting up bullet trajectory rods. Nick sets up a 3rd tech 3-D laser scanner and Catherine finds two long brunette hairs on a pillow, but both the wife and daughter were blonde. Nick scans the room and a 3D gridded representation of the crime scene appears on a laptop.
Brass interrogates Annabelle Frost, 24, a brunette. She is devastated to hear that the entire Stewart family has been wiped out. She was Morgan Stewart's assistant for two years and claims that she never slept with Morgan. When Brass asks for a sample of her hair, she tells him to get a court order. She's pre-law and knows her rights.
In the Layout Room, Greg runs a hydrocarbon detector over the scraps of clothes found on the burn victim. He finds a partially melted plastic card. Greg tells Grissom that there are traces of alcohol all over her clothes; she was doused with it. Grissom realizes that she was the cause of the fire.
In the CSI Print Lab, the handle of the vodka bottle is processed in a cyanoacrylate tank and a print is found. After a run through AFIS, a match is found: Patrick Bromley, a man in his 20s.
Sara tells Grissom that Bromley is a truck driver and she was able to get his route data for the past 24 hours. They analyze the GPS coordinates on a computer and find that he was in the area of the fire an hour before the alarm for it went out. Additionally, he stopped at the local "gas n' sip" a half hour before that. Surveillance footage is already on its way.
At a truck stop, Sara and Detective Vartann find Patrick Bromley and confront him with video footage of himself walking to his rig with a bottle of vodka. Inside the cab sits a woman in a pink sweater.
Bromley claims he picked her up hitchhiking and never got her name. He dropped her off on Blue Diamond Road. Sara notices Bromley has scratches on his neck, which he claims came from a bar fight.
Sara climbs into Bromley's truck and searches the cab section behind the seats. Amongst the mattress, dirty blankets and cigarette butts is a pink sweater.
In the Interrogation Room, Bromley claims he just helped the "chick" out. He didn't sexually attack her--he's a happily married man. After the CSIs accuse him of pouring vodka on the woman and setting her on fire, Bromley asks for his lawyer.
In the CSI Hallway, Warrick tells Catherine and Nick that bullets found at the Stewart house match the gun, which belonged to Morgan Stewart. Stewart was in severe debt and they speculate that it may have been a murder-suicide.
In the Coroner's Office, Dr. Robbins explains the trajectories of the bullets that went through Morgan's head and Corinne Stewart's back. The daughter died of drowning, the only trauma being a broken rib, which could have been from the EMT's CPR except she had the injury when they found her in the pool. Catherine speculates that it all could have started with the death of little Dani, tipping Morgan's already financially-stressed state of mind. He could have shot Corinne as she tried to escape down the stairs and then shot himself. This theory would work except "Why perform CPR on your daughter and then toss her back in the pool?"
Mia tells Grissom that one of the burn victim's DNA markers is "out of the control range," which is an anomaly that occurs with a frequency of one in every 250.
In the CSI Evidence Room, Greg uses the video spectral comparator 2000 system to find information on the melted piece of plastic found on the burn victim--she is Tara Matthews.
Grissom and Greg talk to Neal Matthews, 32, about his wife, Tara, who he last saw the night before at around six o'clock. They had a fight and she left. Tara had been on anti-depressants. The CSIs tell him his wife has been in an accident.
That night at the Hospital Burn Unit, Greg stands next to Neal Matthews as they look through a glass partition at the heavily bandaged body of Tara Matthews. He claims it is not his wife, but then Greg shows him the wedding ring. Neal recognizes it and realizes it is his wife.
Later in the CSI Layout Room, Greg stares at Tara Matthew's amputated fingers in a glass jar. Greg is obviously disturbed by the case. Grissom tells him he will take over as Greg has pulled a double shift. Grissom analyzes the fingers and finds a shiny green substance embedded in the charred skin.
Mia analyzes the bed sheet from the Stewart house, running ALS over it and finding several sex stains. Catherine notices Hodges watching Mia from a distance and says, "Hard to look and not touch, huh?" Hodges tells Catherine that the brunette hairs found on the bed were not a match to the wife and that the broken glass found on the bedroom floor is from a BBT, a basel body temperature thermometer, used during ovulation. It looks like Corinne Stewart was trying to have another child.
Mia shows Grissom and Catherine, on a computer screen, Tara's DNA alleles, which are abnormal. Most of the population has alleles 12 through 19 on locus D3 whereas Tara has a D3 profile of 15 and 21. The DNA profile matches the DNA extracted from the vaginal contribution found on the sheets from the Stewart house--Tara Matthew's DNA was in Morgan Stewart's bed. "We're working on the same case," states Grissom.
Grissom, Sara, Warrick and Catherine determine that the high density polyethylene found in Tara's fingers is consistent with material that plastic disposable lighters are made from. They deduce that the lighter blew up in her hand and that Tara must have set herself on fire.
Warrick tells the CSIs that according to Brass, Neal and Morgan have been friends since childhood. They posit that Morgan may have been jealous of Neal's financial success and slept with Tara out of spite. Grissom points out that if Morgan shot himself, he is the prime suspect for killing Corinne. If he was murdered, then someone else must have been in the house.
Brass finds Neal Matthews in the Burn Unit at the hospital and tells him that his wife, Tara, was having an affair with Morgan. Brass asks him what would have happened if Morgan rejected her. "Would she have reacted badly enough to kill?" Neal answers, "Not Tara."
Nick is in the A/V Lab working on the computer 3D scan that he made of the crime scene. He shows Warrick the trajectory angles and they realize that Morgan must have been shot on the floor. His body was lifted up to the bed and they never found any initial spatter patterns because the blood puddle under his head covered it up. Somebody else definitely was in the house.
At the Matthew's residence, Sara finds a curved shard of glass in the bottom of one of Neal's tennis shoes in his closet. Meanwhile, Grissom finds a basal thermometer in the vanity area.
Grissom enters Catherine's office and tells her he found a basal thermometer in Tara Matthews' medicine cabinet. Catherine tells him that according to the autopsy report on Corinne Stewart, she had a tubal ligation. They realize that Tara is the one trying to have a child.
Catherine tells Grissom that Dr. Robbins confirmed that Tara Matthews is pregnant. He checked a urine sample from her body. Grissom is surprised that she didn't miscarry. The CSIs realize that Tara was having sex with Morgan in order to conceive with him, "procreation, not recreation." The glass in Neal's shoe places him at the crime scene, but they didn't find any blood on clothes from his house. Catherine remembers the pink sweater found in the truck.
Catherine finds a crusty white stain on the pink sweater and cuts out a sample of the stained fabric.
In the Interrogation Room, Brass tells Neal Matthews and his attorney, Brad Lewis, that they found chlorine from the Stewarts' pool on his wife's sweater. They are going to charge Tara with the murders.
Brass tells Neal that he figures Tara went over to Morgan to tell him she's pregnant with his child. Neal thought it was his, but Brass informs him that according to his medical records his sperm is bad.
Neal breaks down. He tells Brass that he was hanging out with Morgan, having beers, and he got a splinter. He went to Morgan's bathroom to find tweezers and instead he found a basal thermometer. Neal realized that Morgan was having sex with his wife and went berserk. Morgan told him that it was Corinne's idea, but Neal pulled out the gun from a drawer and they fought over it. Corinne was out by the pool with little Dani and when she heard her husband shouting, she ran in to the house, leaving her daughter in the pool.
Neal shot Morgan under the chin and Corinne entered. When she turned around, Neal shot her in the back. Neal found Dani in the pool, so he called his wife, Tara, to help. Tara tried CPR on Dani, but it was too late. Tara ran out the door, claiming that they didn't deserve to live. Neal says, "All we wanted was a baby."
In the Burn Ward, Tara lies wrapped up like a mummy, a ventilator hisses and the heart monitor beeps with regularity. Tara's eyes suddenly open.