Two officers run across a man dumping the body of a woman into a car trunk. They go after him and in the process of climbing a fence in an attempt to flee, the young man is killed. Mac Taylor shops in a convenience store and runs into Ella McBride (last seen in "Dead Inside"), whose mother killed her father. Ella asks Mac out to breakfast, but he gets a call to a crime scene. He meets Danny and Flack by the car; the man the police shot is identified as Tony Clark, while Danny finds car registration forms belonging to Isabelle Vaughn, giving them an ID for their victim. Danny uncovers a bright red stain on the driver's side carpet, and recovers Tony's cell phone with a fresh text reading, "Is it done yet?" There's no corresponding stain on Tony's shoe, suggesting a second person is involved. The bodies are brought to the morgue where Sid begins the autopsies and is shocked to discover Isabelle's organs have literally liquefied. Sid tells Hawkes that both victims consumed some decidedly odd cuisine, from raw onions to dandelions to citrus peels, but Isabelle consumed large amounts of sodium hydroxide, which killed her. Adam tells Danny he discovered the substance under Isabelle's fingernails is elephant dung. He tries to give Danny financial advice, but Danny is distracted when Lindsay comes to tell him the baby kicked. Lindsay heads off to show Mac a discovery she's made: the trace on the car carpet was from a red berry that alters taste buds, explaining the odd cuisine Isabelle and Tony ingested. Flack gets an ID from the phone company for the person who sent Tony the text: Quincy Feeney. The young woman tells Mac and Flack that she barely knew Isabelle, a famous handbag designer. She claims Isabelle's death was accidental and that she and Tony were simply trying to get rid of the woman's body, knowing that her death at Tony's party made them look suspicious. At Tony's apartment, Danny and Hawkes find the primary crime scene in the bathroom, where the sink is filled with Isabelle's blood. Danny finds drain cleaner and wonders if it is the murder weapon.
Ella McBride shows up at Mac's office with one of the postcard confessions from the site she runs that she thinks might be linked to Isabelle, featuring her trademark logo with the words "I want her dead" on the back. Mac and Flack question Marina Morton, Isabelle's business partner whom she was suing and about to break away from. Marina scoffs at the idea of Isabelle as a threat, and claims she made Isabelle who she was. She denies any knowledge of the postcard. Back at the lab, Hawkes discovers the sodium hydroxide that killed Isabelle was mixed in a blender. He also learns it was pure; meaning the drain cleaner Danny found wasn't the murder weapon. Hawkes is befuddled when the genetic analyzer is unable to get a read on Marina's DNA, and he takes the machine apart to recalibrate it. Adam has analyzed elephant feces found in Tony's apartment and managed to trace them to a man named Colby Fisher, who uses the material in making recycled paper. Danny and Flack pay the man a visit, and he admits to trying to get Isabelle to eat the material as a prank at the party. Danny notices sodium hydroxide on a shelf and takes a canister for analysis. Lindsay analyzes the card Ella brought Mac and finds evidence Ella herself made it, confirmed by Mac when he runs a handwriting analysis on a doodle beneath the other material on the card. Mac angrily confronts Ella, who tells him she was lonely and just wanted to see him again. Mac leaves angrily after telling her she wasted precious time on the case. Danny matches the sodium hydroxide from Colby's paper plant to the substance that killed Ella and he and Flack interrogate the paper maker. Colby admits to having a relationship with Isabelle that ended when he cheated on her with her business partner, Marina. He adamantly denies killing her. Hawkes figures out the mystery of Marina's DNA: a leaf she ingested that dissolves DNA. When the CSIs find traces of the leaf on the blender and realize Marina's affair with Colby gave her access to his sodium hydroxide, they realize they have their killer. Marina arrogantly tells them she killed Isabelle for defying her. Mac gets a call from Ella McBride, clearly in distress. He rushes to her apartment and finds she's sliced her wrists; he bandages them up and takes the distraught young woman to the hospital, passing by a secret that reads, "I will make him love me."
Stella has a case of her own: Angell calls her to a pawn shop where owner Declan Rooney has been murdered in the exact same way Wolford Bessie was killed (in "The Cost of Living"). Stella is convinced that Sebastian Diakos, an antiques dealer she met at the Greek embassy, is behind both murders. Sid confirms the killings were performed in the same manner, and Mac posits that the murderer had special ops training. Stella examines an empty piece of display felt she found at the scene and finds an impression of a Greek coin, which she shows to Danny. Danny recognizes it as the same Philip II coin they recovered from an amulet in the previous case. Angell introduces Stella to Stan Travado, an ex-con who went away for counterfeiting coins. In exchange for getting his brother, Marty, transferred to a different prison, Stan agrees to make 20 counterfeit Philip II coins for Stella. When Mac gets wind of Marty's transfer, he orders Stella to drop the idea of trying to trick Diakos with the fake coins. Stella storms out of Mac's office. Later, Angell meets with George Kolovos from the Greek Embassy offering to sell him a batch of the coins and showing him one of the fakes as proof. After she has him hooked, she rendezvous with Stella in a car outside the restaurant and tells the CSI he took the bait.