The team tries to find a bike messenger -- who has kept a video diary of his troubles with women -- before he can commit another violent act; the new deputy chief calls Benson's leadership into question.

A measles outbreak delays arrests in a case involving pornographic photos taken by teens at a party. Meanwhile, Benson discovers that some kids' medical records may have been falsified after Noah gets measles; Amaro leans upsetting news about his son.