A woman's electronic devices start to go haywire in her home. She opens a bedroom door to discover that a fire is raging.
Meanwhile, Mundo is chasing down a black hat informant name Rusty who the team believes is giving away information about them. Rusty gives Avery what he calls a hot piece of code.
Mundo and Avery interrogate Rusty about where he bought the code from.
Mundo has an argument with his ex-wife about who their daughter Michelle will live with.
Avery suspects that someone who has the wifi code must have started the fire as an act of arson.
Nelson pays a visit to his black hat friends and reclaims a flash drive that he hid in the bathroom. Krumitz identifies the IP address that hacked the victim's wifi and Mundo arrests him.
Avery interrogates the suspect and he tells her that he got the code from someone in a forum.
Nelson reveals to Avery that he was the one who wrote the code that is causing the fires.
When a second fire takes place Avery believes that the crime does not fit the first one. Mundo snaps at Krumitz and Avery chastises him for it.
The hacker causing the fires releases a threat to Avery warning them against taking the printers offline. Avery and Krumitz discover a message the Nelson sent to the hacker and discover that he know who he is.
Mundo and Avery discuss whether Nelson will betray them or not. Mundo mentions that they were betrayed in the past.
Nelson tries to save his friend, but chooses to stay with the FBI in the end.