Mandy Lang was a young girl who appeared in season 2. She joined Joe Carroll's cult when she killed her mother Judy Lang. Seeing a father figure in Joe, Mandy followed Joe in his goals and became a follower for Joe and, along with Emma Hill, was one of his most loyal followers before her defection to Lily Gray, which resulted in her death.
Mandy is first seen calling out for "Daryl", who is really Joe Carroll in hiding about the news of the subway massacre. After a local priest comes to meet her mother, Judy, who is a prostitute, he attempts to leave after discovering of Joe's identity. However, Mandy helps Joe apprehend him and watches uncomfortably as Joe kills him.
Joe reveals to Judy and Mandy his plans to leave their home at night as Judy expresses her resentment for Joe murdering the reverend. She pulls a gun on Joe but he had previously taken out all of the bullets. He attempts to choke her to death but stops when Mandy begs for him to. Joe ties Judy up, setting up a crime scene implicating the reverend for when the police discover the home. Joe looks for his knife, but Mandy finds it and proceeds to stab her mother to death, not wanting to lose Joe. Joe sets the home on fire before departing with Mandy.
Joe and Mandy sneak into the house of a young mother with two children. The mother, Jana is revealed to be a friend of Joe and provides him with a fake ID and cash. When Joe calls Emma, she hesitantly tells him that it is safe for him to come there. Joe arrives and upon embracing Emma, she bursts into hysterical tears before he moves on to meet the rest of the group and Mandy. Mandy is later taken to Lily Gray's home with the others.
After Luke's capture by Ryan, Mandy and Emma help find and unconscious Joe and wake him up. Enraged at Lily, Joe leaves after killing her daughter with Mandy and Emma watching as Mandy seemed scared. They managed to elude Ryan and the FBI thanks to Jana's help. Mandy later listened to Joe express his contempt to Lily on the phone while seeming uneasy about his cruelty to her.
Joe, Emma, and Mandy arrive at a cult compound. Two authority figures, Robert and Julia, have them blindfolded and handcuffed before entering the trucks. While Joe says it will be okay, both Emma and Mandy do not like the Korban cult. Later, after Emma is almost killed, Mandy was seen rolled up scared over what happened. Later, after interacting with a boy Mandy liked, she was horrified to see the Korban leader Micah kill him and 4 others.
Once Joe became the new cult leader, Mandy slowly began to lose her faith in him. After witnessing him preach about murder and doing blood annulments, Mandy attempted to leave and was almost put in the hole with the other doubters, but Joe gave her a second chance. However, she and Emma get into an argument to which Emma states Mandy will disappoint Joe and should watch herself, to which Mandy notes Emma is jealous and warns her to watch herself to.
After Mandy sees Joe kill a Korban member and forces another one to kill her, Mandy again begins doubting Joe. This, coupled with listening in on Joe and Emma's talk about Joe's disappointment with Mandy and viewing her as a lost cause, causes Mandy to eventually leave Korban. She is picked up by a driver and makes a call out to non other than Mark Gray. She is then found by Mark along with his body guards, making Mandy nervous. Even more so after he asks about Joe's location. Mandy however says she can't, but Mark says he understands.
She is then taken to Lily's home, to which Lily admits she's happy to have her (though it's obvious she's just faking it to get Mandy to drop her guard). As she lets Mandy into her home she tells Mandy of her desire to travel with her family, but lost all that chance after they were murdered, to which Mandy apologizes since she felt she had no choice. Lily says she understands and just wants to know where Joe is as she wishes to talk with him. Mandy says she views Joe as a father and can't betray him. Lily slaps her and, dropping the nice act, demands Joe's location. Mandy attempts to leave only for Mark and Luke to stop her.
They force her in a game of "truth or dare", to which Mandy tearfully begs them not to do what she knows they will do to her. When the bottle points to her and they ask which she chooses, she does not answer and they view it as "dare" and burn her arm with a lit candle. Mandy screams in pain and begs Lily to help, but Lily ignores her cries for help. Mandy is then left brutally beaten to a bloody pulp by the twins and Lily reveals a call from Joe to Mandy. Mandy weakly reveals she didn't tell her anything and Joe says how foolish it was for her to have left but asks Lily to let her go. Lily says she will if Joe gives himself up if he loves Mandy. Joe can only say "I love you Mandy" and Mandy responds the same, crying over having been abandoned by the only father figure she ever had.
She is later finished off by the twins and has her corpse strapped to a chair with the twins and Lily as they eat dinner and "talk" to Mandy's dead body. Her deceased body is later found during an initial raid by the FBI after Lily, the twins, and Lily's hired hit-men fled and abandoned the house to pursue Lily's attempt on Joe's life after finally discovering his location that Mandy originally refused to divulge.
Mandy is a rather complex young woman. As while she is loyal to Joe, she does not seem all too comfortable with killing people like Joe or his other followers are. However, she had no qualms in murdering her mother in order to protect Joe, viewing him as the father she never had. Mandy also tends to be more nervous in situations as apposed to Joe or even Emma, to which Mandy questions whether they will be caught or not.
Despite being a follower, Mandy seems to be hesitant to murder people. After watching Joe try to manipulate the Korban followers, Mandy was among some to have left, not wanting to agree in Joe's teachings, though she was later given a second chance by Joe. It is this that causes her and Emma to become antagonistic towards one another, to which Emma views her as weak. Mandy however, has shown to have some ruthlessness in her, having warned Emma to not underestimate her, having told her "you're not the only one who murdered her mother", showing she has no remorse in killing her mother.
However, after witnessing Joe kill a Korban member to influence others to kill, coupled with Mandy hearing of Joe viewing her as a lost cause, Mandy has left Joe's cult, further displaying her lack of interest in killing. However, she did still have her love for Joe as a father figure, refusing to betray him even after being tortured by Luke and Mark and even after dying at their hands.
Mandy appeared to have been someone who could not take care of herself, having left Joe after seeing the power go to his head only for her to go to Lily and her sons. This however, coupled with Lily's contempt for her and Joe, resulted in Mandy's death as she believed Lily would forgive her but resulted in her being tortured by her sons and later killed after discovering that Joe would not go to save her.
- Judy Lang (her mother; stabbed repeatedly)