When a well-known cancer researcher is found dead, Watson and Holmes must determine if his death was related to his latest invention; Bell is finally allowed to re-enter the field.
Danny considers retiring until Erin asks for his help with a case involving her ex-husband; Jamie and Eddie pose as a couple; Frank clashes with the new mayor.
A severed hand and foot are found in an alley; Megan allows Lacey to film her at work for a school project.
Alicia and Diane agree to let a famous liberal lawyer (Jeremy Breslow) aid them on their latest case, but they soon realize he may not have their client's best interests in mind. Meanwhile, Alicia's mother (Stockard Channing) arrives for Thanksgiving seeking moral and legal support from Alicia and her brother Owen. Brian Dennehy returns as Lawyer Bucky Stabler and Bebe Neuwirth returns as Judge Friend.
Erin must convince Frank to back a new state police bill as part of a bargain she made with Gov. Mendez; Danny and Baez pursue the same perp twice after the DA's office is unconvinced by their initial lineup; a cop killer comes up for parole.