| 12.01 | 73 Seconds
|  Multiple shootings and stabbings on a public tram leave the CSI team with one witness and a lot of questions.
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| | 12.02 | Tell-Tale Hearts
|  Three suspects come forward with three different reasons why they killed an entire family and the CSI team has to determine who is telling the truth.
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| 12.03 | Bittersweet
|  While on a date, Stokes realizes a piece of art at an exhibit has decomposing body parts in it, which leads to a full-blown investigation. Also. D.B. Russell makes a decision to ground one of the staff from the case.
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| | 12.04 | Maid Man
|  The former Mayor of Las Vegas is shot at the Mob Museum and the CSIs embark on a history lesson in search of clues.
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| 12.05 | CSI Down
|  When a hijacked medevac helicopter with CSI Brody aboard goes missing, the entire tam is on the hunt.
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| | 12.06 | Freaks & Geeks
|  When a Jane Doe is found near the freakish attractions of a 19th century-inspired traveling sideshow, the team investigates a cast of unusual characters.
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| 12.07 | Brain Doe
|  When the CSI team arrives at a car crash, they find three casualties and a human brain that doesn't belong to any of the victims. Also. D.B. Russell is concerned his son is not focused on college following his suspension from school.
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| | 12.08 | Crime After Crime
|  When the CSI team investigates three seemingly unrelated murders, they discover someone is getting revenge for cold case murders that were never solved.
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| 12.09 | Zippered
|  When the CSI team discovers a deceased rancher was also a ballistics expert, they have to work with the FBI to solve the case.
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| |12.10 | Genetic Disorder
|  When the body of a naked dead man is discovered by Dr. Robbins' wife in their master bedroom, it leads to a lot of questions for the CSI team.
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| 12.11 | Ms. Willows Regrets
|  When Willows works with the FBI again after a professional hit occurs at a law firm she recommended to her friend, the CSI team identifies shocking similarities at the crime scene.
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| 12.13 | Tressed To Kill
|  When a woman is found dead and her hair is done up '70s style complete with vintage clothes, the CSI team discovers clues that point to a killer with a hair fetish. |
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| | 12.14 | Seeing Red
|  Russell seeks advice from a former colleague during an investigation into the death of a man's ex-girlfriend. |
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| 12.15 | Stealing Home
|  When a house is stolen completely off its foundation, the CSIs are on the case in search of answers. Meanwhile, new CSI Julie Finlay showcases her skill in blood analysis. |
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| | 12.16 | CSI Unplugged
|  When a blackout cripples the city, the CSIs must revert to old-school methods to solve the case of a missing child.
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| 12.17 | Trends With Benefits
|  The CSIs are brought in to solve the case of a recently murdered student whose death photo ends up trending on the Internet.
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| | 12.18 | Malice In Wonderland
|  (When the CSI team is called in to investigate a robbery-homicide at an "Alice in Wonderland" themed wedding, they have little to work with to find a killer. Meanwhile, Hodges' mother comes to town and he wants her to believe Morgan is his girlfriend.
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| 12.19 | Split Decisions
|  When the CSI team is called in to investigate a man who is short at point-blank range in a local casino, they shut down the entire building to find their killer.
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| 12.21 |
| (Synopsis) |
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| | 12.22 |
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CSI Season 12 Episode Guide
The CSI team says goodbye to Catherine Willows as she makes a life-changing decision.