Starts with Santana, Blaine and Kurt as juniors and as three best friends in high school (I think Kurt has unspoken/unrequited feelings for Blaine)
Sebastian’s brother is the sub for WMHS Glee club (Schue broke his leg or something)
Blaine meets Sebastian when Sebastian comes in to the school to meet his brother. I think he is a couple of years older than B/K/S
Blaine and Sebastian fall for each other
Sebastian is singer and gets Blaine in as a backup singer
Kurt walks in on Sebastian and Blaine in a compromising position, and is heartbroken
Due to many factors Blaine accepts a back up singing position on a world tour that will take him away from his senior year, his relationship with Kurt is strained at best.
Blaine withdraws from his HS friends while on tour, trying to keep his relationship with Sebastian afloat and starts to abuse alcohol and becomes somewhat promiscuous.
Meanwhile, Kurt begins a friendship, which ultimately develops into more, with an older man (a chef) who he met at a gig of Blaine’s
I think there is a time jump; eventually Kurt (a designer) and Santana (a singer) are in New York and have an eccentric lovely older lady neighbor. They run into Blaine at a performance of Santana’s, Blaine is now in recovery.