|Pathology|| Serial assailant|
|Family|| Tom Mesner (father)|
Viola Mesner (mother)
Ruby Mesner (sister)
|First Appearance||"Born Psychopath"|
Henry Mesner is a 10-year-old suspect in his sister's physical abuse.
At school Henry's sister, Ruby is taken to the nurse and find bruises on her stomach and a bump on her head. Ruby admits to the SVU detectives that she got those bruises from being pushed by the "Monster". Henry says that he was eating waffles in the other room and didn't know that Ruby got hurt. The SVU squad discovers that Ruby has a history of multiple injuries and emergency room visits in the last year. When Henry is questioned about what happened to Ruby, he says that he saw Irina, his family's babysitter lose her temper with Ruby and pushed her down the stairs out of anger because she was being difficult.
When Irina is questioned, she says that Henry was the one that pushed Ruby down the stairs and is the "monster." When Olivia and Nick talk to Viola about it, she admits that Henry resents Ruby and they had to see a counselor because of it. When Henry is questioned again, he admits that he pushed Ruby as a kind of "experiment" and is convinced she wasn't hurt because she didn't cry much. Henry's father, Tom is convinced that Henry's behavior is normal for his age and believes he just needs to find a hobby and work out the problem amongst himself. Tom and Viola (Henry's mother) don't want Henry to see a psychiatrist because they're afraid that Henry might get labeled.
The SVU squad comes to the conclusion that Henry needs help. The detectives at first talk to Corporation Counselor Pippa Cox and tell her that Henry's family is in possible danger. Pippa disagrees with this and says that home is probably the best place for Henry. Olivia hotly disagrees, arguing that Ruby was very clear that Henry pushed her down the stairs. Pippa hotly asks Olivia if she wants every big brother locked up for pushing their sister and hotly says that Henry is ten and that there will likely be inconsistencies when the story is asked several times. Tutuola calmly asks about another solution for Henry, to which Pippa says if they want to give it a go, it's up to them.
Olivia and Rollins tell the Mesners that there will be no charges pressed against Henry if they agree to take him to see a shrink. Viola assures them that she will care for Henry and make sure he is not left alone with Ruby. Viola tries to tuck Henry in for bed, but he refuses to sleep, taking a knife from behind his pillow. Viola demands for Henry to hand over the knife, but Henry slashes the knife across her palm when she reaches for it and watches as she runs away, looking upon her with blank, emotionless expression.
When Olivia arrives at the hospital where Viola's wound is treated, Viola defends her son, saying that it was her fault. At the Mesner residence, Rollins looks on as Tom reprimands Henry for hurting his mother, but Henry angrily lashes out, saying that it was Viola's fault. Henry's outburst wakes Ruby and Rollins tells Tom take her back to her bedroom while she stays with Henry. As Tom takes Ruby back to her room, Henry makes small talk with Rollins as if nothing happened at all.
When Dr. Huang evaluates Henry, he tells the SVU squad that Henry is a psychopath because he lacks any emotions and doesn't feel any sympathy or empathy for other people. Dr. Huang suggest sending Henry to a facility in Vermont for severe cases like his. At first, the Mesners balk at the idea, but eventually agree. When Viola tells Henry about the facility, Henry once again throws a tantrum, but calms down when Tom leaves for work. Henry locks Viola in the laundry room and lights a fire. Henry ties Ruby to a bed and watches her cough to see if she would burn inside out, but after the room is filled with smoke, he calls Olivia.
By the time the SVU squad arrives, Henry has already left the apartment and went to his friend, Toby. Henry steals Toby's father's gun and locks him in a closet and kills his dog, Snowball, by drowning him in the bathtub before leaving. When Nick goes to the play area of the apartment building, he notices Henry has taken a five-year-old boy hostage using the gun of Toby's father. Nick is able to talk Henry into letting the little boy go, but Henry points the gun at Nick & asks him to stay. As Nick tries to talk Henry into giving up the gun, Henry shoots him in the stomach, but Nick is able to wrestle Henry to the ground and restrains him as Olivia arrives with backup. Because Nick was wearing his vest, he only sustains a minor injury to his stomach.
Because Henry cannot be tried as an adult for the attempted murders of his sister and a police officer, Pippa Cox and the SVU tell Henry's parents that he will be charged with juvenile delinquency and will be locked up until he is 18 years old in a secure facility. Viola and Tom tell Henry the bad news. (SVU: "Born Psychopath")
- Unknown dates: Several unnamed classmates (all assaulted)
- 2012-March 2013: Ruby Mesner (his sister; abused repeatedly; later attempted to suffocate)
- March 15-16: Viola Mesner (his mother; assaulted; cut her hand with a knife)
- March 16: The apartment standoff: