Donna Tartt, from The Goldfinch (2013)
new game plan called shield yourself at all times and never let anyone in . this will have no repercussions
Theo Decker
hey man I found a piece of your soul stuck in the text messages of old friends you don’t speak to anymore. do you want it back
A lot of people seem to cite Boris as the character who gets Theo into drugs and kind of brings about his subsequent drug addiction, but this is ignoring that by the time he meets Boris, almost every adult who is supposed to take care of him has already drugged him.
Page 111, "Mrs. Barbour had started giving me a little green pill called Elavil that she explained would keep me from being scared at night...(it strikes me now, though it didn't then, that Mrs. Barbour was well out of line by giving me unprescribed medication on top of the yellow capsules and tiny orange footballs Dave the Shrink had prescribed me.)"
His caretaker, Mrs. Barbour, teaches him that he should treat his grief with drugs. His mental health care team assigned by the state treats his grief with drugs (I think Xanax, which is pretty addictive.) Granted, he's in therapy at this time as well, and I'm not trying to malign the sometimes necessary decision to put minors on prescription drugs for mental health, but combined with Mrs. Barbour, it contributes to the sense that adults give him drugs for being sad.
Page 218, just a couple hours into his father's custody of him (and after his father and Xandra have already once let him get drunk), his father and Xandra see he's scared in the airport, link it (partially correctly) to his trauma from the museum explosion, and conclude:
"Why don't you give him one of those, you know."
"Got it," said Xandra smartly, stopping to fish in her purse, producing two large white bullet-shaped pills. One she dropped in my father's outstretched palm, and the other she gave to me.
By the time Theo meets Boris, every adult responsible for him since his mother's death has seen his grief and trauma, and told him, through their actions, that medication is the answer.
When Boris gives him alcohol and drugs, he's doing it for similar reasons, (page 333-- "I slightly wished we had picked another night to take them, but Boris had insisted it would make me feel better." and page 351, offering him coke, "It'll make you feel better!") But Boris is about the same age as Theo, and, like Theo, has learned to self-medicate from the adults around him. Out of everyone who offers Theo drugs (actual prescriptions from Dave aside in this point), he's the only one who believably doesn't know better.
But one key difference is that Boris, of all the people who give him drugs, is the only one who really engages with and witnesses Theo's grief and trauma. Getting drugs from Mrs. Barbour and from his father are both intended to dampen his outward symptoms because they are inconvenient to others. It's to help him push everything down. When Boris gives Theo alcohol, it actually brings out his true feelings, and Boris never seems inconvenienced by this or unwelcoming of it (page 280-281, "Sometimes, in the night, I woke up wailing...Happily, Boris never seemed annoyed or even very startled when I woke him").
So, while Boris imparts bad drug and alcohol use habits to Theo, he's not the one who gets him started self-medicating. Of all the people around Theo, he has the most limited resources by far (financially, psychological coping mechanism-wise, etc). In fact, he needs help himself that he never really receives. Despite this, he's the only character who really hears Theo's experience and offers all the resources he does have to help.
I love that they have their subgenres of nerd. Like Will is the only one of them who knows morse code but Dustin knows more D&D lore off the top of his head like the details of shadow walking while Lucas is better with like aerodynamics (you can't tell me he's not being nerdy about those wristrocket angles) and like battle prep with all the random stuff in his bag and Mike's the one who says shit like "blasphemous" and "conspiring" in casual conversation.