The scene opens, and while viewing the interior of his home through security cameras tied to an application on his Smartphone, Greg Lux discovers his father's body; much to his shock and horror. Investigators suspect a home invasion gone wrong when they discover Mike's throat was sliced in quite a gruesome manner, severing his carotid artery; resulting in his demise. During a sweep of the crime scene, Greg repeatedly calls his mother's cell phone; so as to confirm where she is and if she is fine. As Greg continues to call his mom's phone in a desperate attempt to reach her, Curtis notices Greg's trophies, commenting to Greg that his dad must have been very proud, that he had won so many. Greg explains he would never have the trophies without his father's help and that they were all thanks to him that he managed to win so many.
Dr. Hunt asks Greg for a DNA swab for elimination purposes, so they can move on to other suspects, causing Greg to hesitate and appear slightly flustered, which immediately fuels suspicion. Requesting to wait until he speaks with his mom, he continues to call her phone until Curtis hears the faint buzzing of a phone, leading Dr. Hunt and the detectives to discover Greg's mother, Robin, dead in a closet upstairs. Is Greg suspect number one, possibly due to how things have just turned out? While Kate and Megan try to decide Robin's cause of death, and what caused a rash on her face, a second suspect emerges, Michael Lux's business partner of 10 years, Mr. Kruger. He explains to Detectives Morris and Baker he had known Mike for years, even introduced Mike to Robin. Mike was the most driven person he had ever met; he just wishes Mike had opened the safe.
Morris and Baker comb the crime scene for clues, hoping to find something that would further aid their investigation. According to the insurance records, six pieces of jewelry are missing, which could clearly be the motive for the crime. Whoever has the jewelry could be the killer, from the look of things. Morris also notices a plumber's business card on the bulletin board in the victim's kitchen, the same business card found in two other home invasions, so that too might be a possible clue to the murders. Thus suspect number three emerges, based on the evidence at hand. Megan discovers a substance in Mike's neck wound apparently from the serrated blade used to slice Mike's throat and sends it for analysis, in order to find out more about it. Kate announces Robin died of asphyxia, but only her mouth was covered with duct tape, which clearly can’t be a possible reason for asphyxia.
During the autopsy, Kate discovered Robin's sinuses well swollen; cutting off her airway, hence that was the real cause of her death due to asphyxiation. Since Robin wasn't suffering from a sinus condition, what caused her sinuses to swell? It instantly dawns on Kate and Megan that Robin's rash was an allergic reaction, but to what? The plumber is brought in, and is questioned about his involvement. Bud and Samantha show him pictures of the crime scene and tell him the police are sweeping the house for DNA and fingerprints, but the plumber has nothing to say; he seems totally at a loss, and supposedly hasn’t a clue about things that have transpired in that house. Peter Dunlop and Megan view images of Robin and Mike's injuries side-by-side, and stumble upon something. I turns out the marks made on Robin's arm by the duct tape are not as severe as Mike's.
Megan surmises the killer knew Robin and didn't mean to kill her, but just restrain her. The killer must have cared for Robin, and thus had probably wanted to spare her. Lab results show Robin's allergy was caused by a mixture of sea salt and lemon juice. The same ingredients are often found in metal polish and used in high-end jewelry stores. Suspicions fall back on Mike's partner, Mr. Kruger; as the present evidence at hand indicates the same. Bud has discovered Mike wanted to dissolve his partnership with Mr. Kruger, and Megan confronts him about his feelings for Robin; much to his surprise. Did he kill Mike to have Robin for himself? Megan pushes, telling Mr. Kruger he caused Robin's allergic reaction, killing her by accident. He admits that he was in love with Robin. He claims Mike wasn't good to Robin, and he had sucked the life right out of her.
But at the end of it all he insists, he is not the killer; despite the feelings that he had for Robin he would never do such a thing. Analysis on the duct tape covering Robin's mouth sheds light on a fourth subject, Robin and Mike's unknown son, Aaron, who wasn’t in the picture till now. A runaway, Mike removed all traces of Aaron from the house, as he probably didn’t want to have anything to do with him. Aaron emerges while trying to pawn some of his mother's jewelry and is immediately taken into custody. Questioning Aaron, Samantha suggests he came back to prey on his family because he couldn't make it in the real world; and in the process ended up murdering his parents. Aaron refutes this allegation and explains that he disappeared because he couldn't meet his father's expectations; his dad beat him because he was never good enough, and that was the whole reason for him taking off in the first place.
Bud is suspicious as Aaron tells Bud his mother was scared to death of Mike and so was Greg. Robin stayed in touch with Aaron behind Mike's back, giving him jewelry to pawn; in order to help him out financially. It was the only way she could help him because his dad counted every penny, and thus it would have been impossible for her to help him out with money. Aaron admits to wishing his father dead, but claims his innocence. He only regrets leaving his little brother behind. Meanwhile, Curtis and Kate discover bruises all over Greg's body. He tells Curtis his father beat him, which resulted in all the bruises. Did Greg kill his father because he was tired of being hit? While documenting the marks on Greg's body, Megan notices a rash similar to the one found on Robin. Could the killer have touched both Greg and Robin?
Ethan identifies the substance found in Mike's neck wound as Bondo, a product used to fill body dents on cars. Enter suspect number five, Greg's friend Travis who loves to repair cars, and is surely the one who might be using this stuff for his work. Megan, Bud, and Peter pay a visit to Travis where they discover a grease-cutter made mostly of lemon juice and a serrated knife in his tool box. Travis confesses, admitting to being a victim of abuse and knew what Greg was going through, hence he took the drastic measure that he did. He killed Mike to protect Greg, but didn't mean for Greg's mom to die, he thought he could save them.
Travis asks Megan to tell Greg that he is sorry. Later, Greg goes up to his mom and Curtis shows that his brother is there for him. He tells Greg to look at him and says that he is never going to leave him now. Kate likes that Curtis is the Medical Director and Kate admits to the practical joke. Megan goes up to Aiden and tells him that he was right about her being scared. He says that she needs to be able to want to take the chance. She says that she is willing to take the chance. Megan gets home to find the paintings shredded. Apparently Lacey found out about Tyler’s girlfriend. She gives Lacey her stuffed elephant and the episode ends.