Alec and Marisa attend a wedding of the daughter of a mutual friend that's located inside a foreign embassy, where the father of the bride has been ensconced for diplomatic reasons. Their night off quickly turns into a murder investigation.
The FBI needs Alec and his team to help stop a serial killer terrorizing the suburbs.
Simon's mother asks Alec to help stop a suicide contagion when a third student death strikes the campus. Alec ask Marisa to help when he thinks there might be more to the case. Phoebe struggles with her next career move. Rizwan learns about Simon's past.
On the season finale Drill's mysterious endgame is put into motion and the team must do their utmost to stop it before it reaches its final, and possibly deadly, conclusion.
