This episode really impressed me, turning a mundane whodunnit into an actually interesting plot that while somewhat obvious, still has little twists and turns. Even the little gags are either meaningful for its plot, or nice and impactful with where they go.
Zipp is the star, conflicting with the others as she questions them. Izzy however is also there to prove she's got a personality of her own. Even Pipp is made use of well, with her vanity. All these characters come together well and elevate what would otherwise be fairly boring (a series of flashbacks from in one room).
A very good episode in general.