Making her entrance at their party, Amanda Haynes and her husband Patrick Haynes hold a charity fundraising party at the home of Portia Richmond, a retired Las Vegas showgirl; the CSIs are called in when Lacey Duvall is found dead, floating in the backyard pool.Catherine processes the pool and finds a bright red fingernail, while Warrick finds a cufflink with the initials “CM”. In autopsy, Doc Robbins notes that Lacey was strangled.
While checking Portia Richmond's music boxes for fingerprints, Grissom and Willows hear noises coming from upstairs. They discover the source of the noise in Portia's bedroom and awkwardly catch the Haynes couple in the middle of a sexual session. Afterwards, Brass questions the Haynes and learns that although Portia is on vacation, the couple was hosting the party on her behalf. During the interview, Amanda sips water through a straw, and Grissom asks for it claiming he collects straws as a hobby; Amanda willingly hands it over. Grissom and Catherine then search Portia’s bedroom and find no evidence that she packed anything for a trip. However, they do find a human tooth in the fireplace, and DNA confirms that it belonged to Portia.
Grissom returns to the morgue and sees that one of the finger marks on Lacey’s neck is less vivid than the others, implying that the strangler had a broken fingernail. Greg processes the fingernail collected at the house for DNA, and learns that the owner of the fingernail is related to Chad; he matches the DNA to the DNA from Amanda’s straw, suspecting the murderers are first-degree relatives.
During questioning, Chad/Patrick admits to having a relationship with Lacey in the past but broke up with her after he fell in love with Amanda and even cheated on Lacey so he and Amanda would be together. Grissom then confronts him with the evidence that his wife Amanda is also his sister, and informs him that Amanda killed Lacey.
The night of the fundraiser party for Portia Richmond, Lacey confronted Amanda, claiming that Patrick still loves her and wanted "no more lies, no more faking love, no more acts". Amanda tells her that her love with Patrick was never an act and is as real as it can be. Lacey then blackmails Amanda by saying his real name and holds the turquoise cufflink with his initials, claiming it's her turn to become like Amanda and force Patrick to stand by her both criminally and romantically. Angered by Lacey's attempt to steal Patrick back from her, Amanda snatches the cufflink out of Lacey's hand and throws it into the pool, then clutches Lacey by her throat, breaking off one of her red manicured nails in the process. In the struggle between both women, Lacey falls into the swimming pool dead while Amanda goes back to the party acting like nothing's happened. Patrick asked her if she really killed Lacey because he told her the truth about their identities, Amanda admits she had no choice and she only did what she did to protect their relationship. Grissom also tells Chad and Amanda that the piranhas in Portia’s gardenside pool show evidence of having eaten a person due to the high cholesterol within them; Chad and Amanda confess to killing Portia and feeding her to the fish and both lovers/siblings are arrested for the murders of Portia Richmond and Lacey Duvall.
She is married to her biological brother and partner-in-crime, Patrick Haynes.