While Fin and Phoebe make wedding plans, Benson and Rollins try to help a homeless single mother who's being trafficked in exchange for safe housing.
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.
When a student goes missing during a school excursion to New York City, the cops attempt to hunt down a mysterious masked man.
Max, Bloom, and Reynolds recount a patient's past encounter that could throw them into a massive lawsuit; Iggy confronts a local middle school about its teaching policies; Kapoor lets his superstitions take over.