Patrick is one of Charlie's best friends. Though, we only get to see Patrick through what Charlie decides to share in his letters. Charlie says that "Patrick usually isn't unhappy". He's possibly holding a lot of it inside.
Charlie first knows Patrick as 'Nothing'. Their first introduction is when Charlie introduces himself at a football game.
It is later revealed at a party, that Brad, the quarterback of their high school's football team, and Patrick are in a secret relationship. Brad keeps the relationship a secret, because he doesn't want anyone to know he's attracted to men.
After Brad's dad walks in on Patrick and Brad together and Patrick almost gets beaten up by Brad and his friends, his mental state plummets. Patrick turns to drugs and sex to cope. Even as Patrick copes through unhealthy methods, he suffers little consequences. He drags Charlie to the park and other hook-up locations, often leaving Charlie after getting there.
Patrick plans to attend the University of Washington. Charlie says that "he wants to be near the music there."
After Patrick stops turning to drugs and sex to deal with his mental state, he doesn't spend too much time with Charlie, even when Charlie reaches out to him after kissing Sam instead of Mary Elizabeth during truth or dare,
Patrick and Charlie meet in freshman shop class, even though Patrick is a senior. Charlie notices Patrick for his impression of their teacher and because he earned the nickname Nothing (from the teacher in the movie, from the students in the book).
They meet again, properly, at a school football game when Charlie goes to sit beside him and Sam. They begin talking and after the game they go to the Big Boy for a meal, which quickly becomes a tradition.
After Patrick fights with Brad in the cafeteria, he turns to Charlie to help with his mental state. Together, they drink and visit gay bars, parks etc. in the hopes that Patrick will pick up a guy. One day, they go to the golf course where Brad and Patrick used to meet, and shared stories.
Sam's mom and Patrick's dad got married, meaning Sam is Patrick's step-sister. They leave for college the same year, Patrick going to the University of Washington, Sam going to Penn State.
Brad, the quarterback, is Patrick's love interest. Brad is in the closet, and had a cheerleader girlfriend called Nancy, but neither Patrick nor Brad seem to care about it. In the early stages of their relationship, Brad would get high or drunk before doing anything with Patrick, and would then say he was 'so wasted' that he couldn't remember anything.
Eventually, it got to the point when Brad could be with Patrick whilst sober, albeit in secret. One day, Brad's dad catches them together and starts beating Brad with a belt, with Patrick helplessly watching.
After that incident, Brad insults Patrick more than once in the school cafeteria, resulting in a brutal fist fight between Brad and his friends against Patrick and Charlie.