It's Gus's birthday and Shawn gets him the ultimate present. They are both on the VIP list for the fall launch party for Ciao! clothing as the modeling team "Black and Tan". Once in, Gus is excited to see his favorite model, Berlinda Desidovicz (Amber Borycki), and as he goes over to talk to her, Shawn notices one of Ciao!'s owners, Ciaobella Masterson (Amanda Detmer), berate her assistant and throw a green shake onto the ground. Just then, the other owner, Ciaobella's husband Gregor Uwe-Steeb (Mackenzie Gray), gets up to give a speech. He starts by saying he did all the designs for the new line, and then as he reaches down to adjust the mic stand, he's electrocuted.
Shawn and Gus meet models Hassenfeffer (Jilon VanOver) and Bryan Frou (Corey Sevier), who don't believe Shawn is a model. On their way home from the party, Shawn and Gus stop by Henry's to return some boots only to find Chief Vick there with her friend Susan B. (Amanda Pays), who she is trying to set up with Henry. Vick gets a call from Juliet and Shawn overhears that the electrical cable to the mic stand was tampered with. Gregor's death was definitely murder. The cops are having trouble getting any information out of the witnesses, but since everyone that was at the party thinks Shawn and Gus are models, they are already embedded in that world. So Vick hires them on the case.
Shawn moves he and Gus into the loft where all the models live that are under contract with Ciao!. Ciaobella is there with her assistant Emily Bloom (Melanie Lynskey), who seems to be doing all the work for the funeral. Gus says theirs seemed like a weird marriage but Shawn tells him regardless it did last eight years. Shawn tries to question Sigrid (Katharine Murray), one of the models, who tells them to drop dead, and as she leaves, he notices a note in her back pocket. They don't get much farther with the other models, who insist on taking them out to an oxygen bar. The group ends up leaving Shawn behind, who spots Emily going into Ciao! headquarters. He follows her inside and sees a bunch of sketches with her initials on them. She says she's a designer herself but she leaves everything up to Ciaobella and Gregor, or just Ciaobella now, since she's the company's sole owner.
The next day at the funeral, Shawn sees Sigrid place the note he saw earlier into the coffin with Gregor. They were having an affair. Shawn figures Ciaobella found out about it and killed him. But as she goes up to pay her final respects to her husband, she keels over onto the body, dead. Lassiter and Juliet question Sigrid, thinking the model was upset Gregor wouldn't leave his wife, and so killed them both. But Sigrid insists she always knew he wouldn't leave her. He put his wife on a pedestal and wouldn't even let her drink out of her glasses, but she accepted it and loved him anyway. She says the person with the most motive is Emily, who now inherits control over the company. She wasn't their assistant. She was actually the vice president of Ciao!. Juliet goes to question her and finds the once mousy Emily is now fully in control of the fashion house, supplanting her bosses in every way, even drinking Ciaobella's energy drinks.
Back at the Psych office, Shawn is doing research on Emily when he notices Gus wearing a familiar shirt. Gus tells him it's a Gregor Uwe-Steeb original but Shawn recognizes it as one of Emily's designs. He remembers at the party, Gregor taking all the credit for the new line and realizes he and Ciaobella were stealing Emily's designs. The toxicology report comes back on Ciaobella and the only other things in her system besides poison were the ingredients of the energy drink Emily brought to her every day. But when they go to the studio to arrest her, they find her unconscious at her desk. Luckily they got to her in time to pump her stomach and she tells them all she had to eat was some tofurkey jerky and an energy drink. Shawn now realizes what happened and gathers everyone at the Ciao! fashion show. When they get there, a retrospective video is playing that says Gregor and Ciaobella were actually secretly married long before anyone knew and were about to celebrate their tenth wedding anniversary, meaning if they had stayed married any longer, all of their assets would be split down the middle. The video also shows Ciaobella creating one of her early designs, a dress made of lights. Now all the pieces have fallen into place and Shawn takes the stage to announce that it was actually Gregor who killed Ciaobella, even though he died first. He wanted out of the marriage but didn't want to go through a financially crippling divorce, so he poisoned her energy drink mix. But it took a long time for the poison to take effect, because she was bulimic. This also explains why he wouldn't let Sigrid drink out of her glasses. But Ciaobella knew about the affair and used her electrical knowledge to rig the mic stand to kill Gregor. Emily got caught in the crossfire by using the still poisoned energy drink mix. Shawn has solved the case but since all the culprits are already dead, one of his most spectacular reveals ever ends in a whimper.
- As well as the 'crime passionnel' (crime of passion) aspect to the ending, the title also references the combination of stout, such as Guinness, and ale as an alcoholic drink ('Black and Tan'), and possibly the 'Black and Tan' era or movement in the Republican Party.
- As one could expect with any modeling comedy, there are several 'Zoolander'-esque moments.
- Henry's date, Susan, is played by Amanda Pays, Corbin Bernsen's real-life wife.
- Several of the models' names are descriptive of their character, or silly: Sigrid means "beautiful" and is also the name of Sigrid the Haughty, a queen from Norse sagas; there is a character named Frou and a character named Hassenfeffer, possibly a reference to the character Frau Hassenfeffer from Animaniacs; Frou-frou also means "heavily ornamental," and Hassenfeffer is the name of a German rabbit stew.
The gallery for Black and Tan: A Crime of Fashion can be found here.