Provenza and Sanchez attempt to question Mark about his mother. Mark refuses to talk to Sanchez, says it's not fair he's gotta live with Mexicans, and insists he didn't mind living in a car with his mom or waiting for her in the car alone. However, there is a break in the case when Tao finds a library book of Mark's among his late mother's belongings.
Mark loves the book, which was given to him by "Uncle Henry," who turns out to be a white supremacist and member of a Neo-Nazi group and ex-boyfriend of Ava, Mark's mother. The team is stumped on how to find Henry until Rusty suggests telling Mark that his mom is at Uncle Henry's house. After a few minutes deliberation, the team decides to go ahead with this deception.
Rusty expects to be rewarded for his help by being allowed to sit in on Buzz's interview with Hecht, the suspect in Buzz's father's and uncle's murders. Andy advises him to quit pushing and just give Sharon puppy dog eyes. Meanwhile, Mark is thrilled to think he's gonna be reunited with his Mama and warns Sanchez to watch out for the back bedroom in the house.
Julio refuses to allow Mark to be mentioned in conjunction with the investigation because he doesn't want him targeted by the criminals. The team manages to get his address off school records and serves a warrant to a house full of neo-Nazi memorabilia. Henry tries to shoot at them from a trap door under the back bedroom. After a fight he is arrested and the team finds a meth lab where he was hiding. Meanwhile, Mark begs to wait for his mom and promises he will be good if he can see her.
Henry is an uncooperative witness and the DDA is anxious to connect him to his current case against Dwight Darnell, a white supremacist and murderer of eight interracial families. When the cops discover that Henry was involved in real estate scams involving the homes of the murder victims, he gets his link and is able to ask a judge for a continuance. Darnell makes a fool of himself trying to stop this, being rude to his Hispanic assistant attorney (he is representing himself) and making a stupid racist remark about Chief Taylor before learning he is the head of the police department.
Buzz is tough with Hecht and gets some info out of him about an alibi witness, while Dr. Joe helps Mark understand his mother is dead. Rusty is worried about the boy and Sharon promises they will get him help.