The climax to S. E. Hinton's teen novel That Was Then, This is Now, comes in Chapter 10 on the night that M&M is found. Bryon takes M&M to the hospital to be treated for his bad LSD trip. Later that night after Bryon returns home, he finds Mark's drug stash and realizes that Mark may well be responsible for M&M's condition. Mark may be Bryon's best friend, but his drastic personality changes forces Bryon to call the police, knowing that this will put Mark "behind bars for years." With Bryon's mom "sobbing," the "quivering" Mark is arrested, realizing at last that it is Bryon who has tipped off the cops.
"My God, Bryon, you're not gonna let them take me to jail?"
Didn't he know I'd just put him there? (Chapter 10)
The falling action follows when Bryon visits Mark in the reformatory. Mark has changed drastically and hates Bryon for his betrayal. When Bryon reminds Mark that they were once "like brothers," Bryon laughs and says
"That was then, this is now." (Chapter 11)