Darwyn Al-Sayeed is a Muslim ex-con who has just been released from prison and finds his way to an Islamic extremist named Farik, who recruits him to join a terrorist sleeper cell planning an attack in Los Angeles.

Farik and Ilija receive a deadly biological anthrax shipment and prepare for an attack inside a Los Angeles shopping mall.

Farik learns that the money supply filtering in from Mexico to finance Youmud Din ("Judgment Day") has come to a halt. Farik, Darwyn and Christian cross the border to Tijuana, Mexico, and attempt to straighten out their financial problems.

Farik sends biochemical student Eddy Pangetsu (from episode 2) on a flight to Vancouver, Canada, to drive a shipment of real anthrax across the Canadian border and down to Los Angeles.

The Cell members pose as Iraqi insurgents-in-training in order to infiltrate and take over a secure warehouse as a new base of operations for Youmud Din.

Darwyn befriends a pesticide plant worker in order to buy some of his company's product under the table for the Cell while each of the jihadis cope with personal troubles of their own.

When an Afghan boy arrives at the warehouse looking for training as a jihadi, Darwyn introduces him to a more moderate brand of Islam in hopes of steering him away from terrorism.

The Cell buys explosives from a white supremacist militia while Darwyn's new handler, Patrice Serxner, tries to prevent the LAPD from blowing his cover in a conflicting investigation.

The Cell hijacks a chemical truck in preparation for Youmud Din ("Judgment Day") as the FBI prepares to stop them, not knowing that, due to a misunderstanding of the Arabic calendar, the attack will proceed one day earlier than they think it will.

The Cell hijacks a chemical truck in preparation for Youmud Din ("Judgment Day") as the FBI prepares to stop them, not knowing that, due to a misunderstanding of the Arabic calendar, the attack will proceed one day earlier than they think it will.