Mendelson is somewhat older than House, and is probably a "lifer" with no chance of parole. He is noticeably shorter than House, and much less physically impressive than many of the other prisoners. He travels nowhere without his loyal henchmen, such as Sullivan, who perform most of the violence and physical intimidation directed at other prisoners. He carries several prison tattoos, most with racist themes.
House and Mendelson have a co-dependent relationship. Although House has to give Mendelson two of his Vicodin every day, Mendelson and the rest of the Confederates protect House from the other gangs in the prison. As such, House is allowed to keep valuable possessions like his portable stereo, which is clearly marked as being protected by the gang.
However, when Mendelson finds out House is leaving prison on parole, he demands twenty Vicodin as an "exit tax", threatening House and his friends outside prison if he doesn't comply. House argues he's being unreasonable because House will only get 24 more Vicodin while he's in prison, 8 of which will go to Mendelson during his last four days. However, Mendelson says House is resourceful and will find a way.
House approaches Porter, the prison's entrepreneur and scrounger for help. However, the Confederates have already tied up Porter's entire supply.
When Mendelson learns House is having difficulty getting the Vicodin, he steals House's prison cane while explaining that the reason he can't let him off the hook is that his fellow members of the Confederates will see him as weak and try to kill him.
House decides to steal Vicodin from the clinic. He starts a fire and grabs some while Jessica Adams is distracted. However, on his last day, to avoid being caught, he flushes most of the Vicodin down the toilet and asks for protective custody. However, on the way, he realizes what might be wrong with Nick, the prisoner he has been trying to diagnose, and instead goes to the clinic to explain to Adams and Dr. Sykes that Nick has mastocytosis. When they refuse to run the diagnostic test, House realizes he's lost his chance at protective custody and has to face Mendelson. Adams realizes what's wrong and gives him the twenty Vicodin.
House goes to take the Vicodin to Mendelson, but realizes he can get back to the clinic to test Nick. Instead of giving the pills to Mendelson, he throws them in the air, starting a scramble. Mendelson hits House, giving House an excuse to return to the clinic. However, Mendelson is furious and orders two of his henchmen to restrain House while Sullivan knifes him. C.O. Alvarez realizes what is going on, but can't get to House because of the disorder on the cell block. However, just as Sullivan is about to knife House, Sullivan is hit from behind by House's cellmate Curtis Asofa. Asofa also takes out the two men holding House, then turns his rage on Mendelson, pumelling him without mercy. Asofa was then taken away by SWAT members and it is unknown whether Mendelson survived as he was outcold from Asofa's beatings.