Skeleton (II) - S1.E8

Kibre prosecutes an elusive career criminal for the murder of a sleazy ex-cop and the shooting of a detective. As Kibre's office works with Detective Fontana, they discover their prime suspect might also be a producer of snuff pornography. When a sting goes bad and a shocking courtroom development cuts the legs from under her case, Kibre's career teeters on finding why the shootings were committed in the first place.

This crossover starts on Law & Order S15E20 Tombstone (I).